Biology Chapter on Photosynthesis and Genetics
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Questions and Answers

What is the primary purpose of photosynthesis?

  • To release oxygen into the atmosphere
  • To produce ATP directly from sunlight
  • To convert solar energy into chemical energy (correct)
  • To absorb carbon dioxide from the atmosphere

Which pigment is responsible for the green color in leaves?

  • Xanthophylls
  • Carotenoids
  • Phycobilins
  • Chlorophyll a (correct)

Where do the light reactions of photosynthesis occur?

  • Within the thylakoid membrane (correct)
  • In the chloroplast stroma
  • In the cytoplasm
  • In the cell's mitochondria

What is the product of the dark reactions of photosynthesis?

<p>G3P (D)</p> Signup and view all the answers

Which phase of the Calvin Cycle involves the incorporation of carbon into RuBP?

<p>Phase 1: Carbon Fixation (B)</p> Signup and view all the answers

What is the primary reason for the lower efficiency of C3 plants like wheat?

<p>Photorespiration caused by rubisco adding O2 to RuBP (A)</p> Signup and view all the answers

Which plant type opens its stomata at night to minimize water loss?

<p>CAM plants (B)</p> Signup and view all the answers

Which of the following defines Mendel's law of segregation?

<p>Alleles separate during gamete formation (D)</p> Signup and view all the answers

What is a characteristic of codominance?

<p>Both traits are expressed simultaneously (D)</p> Signup and view all the answers

How did Mendel's work with pea plants contribute to genetics?

<p>Demonstrated inheritance patterns with predictable ratios (D)</p> Signup and view all the answers

Which trait is most likely to follow X-linked inheritance patterns?

<p>Color blindness (B)</p> Signup and view all the answers

What is the primary feature of a test cross in genetics?

<p>Homozygous recessive crossed with dominant (D)</p> Signup and view all the answers

What best describes photorespiration?

<p>Occurs when stomata are closed in hot, dry areas (A)</p> Signup and view all the answers

Which factor contributes to increased fluidity of a membrane?

<p>Double bonds in fatty acids (D)</p> Signup and view all the answers

What characterizes active transport across a membrane?

<p>It can occur against the concentration gradient. (D)</p> Signup and view all the answers

What role does cholesterol play in membrane fluidity?

<p>It maintains an ordered structure at all temperatures. (A)</p> Signup and view all the answers

Which type of transport protein uses energy directly for movement?

<p>Antiporters (B)</p> Signup and view all the answers

In hypotonic environments, what happens to animal cells?

<p>They swell and may burst. (C)</p> Signup and view all the answers

What is the primary difference between the leading strand and the lagging strand during DNA replication?

<p>Leading strand does not require an RNA primer while lagging strand does (A)</p> Signup and view all the answers

Which enzyme is responsible for creating RNA primers during DNA replication?

<p>DNA primase (B)</p> Signup and view all the answers

What do Chargaff's rules state about the composition of DNA?

<p>The amount of Adenine equals that of Thymine (C)</p> Signup and view all the answers

What is the role of telomerase in cellular biology?

<p>It lengthens the telomeres to prevent shortening of DNA (C)</p> Signup and view all the answers

Which of the following statements is true regarding DNA replication?

<p>Okazaki fragments are a result of lagging strand synthesis (D)</p> Signup and view all the answers

What discovery was made by Avery, McLeod, and McCarty?

<p>DNA is the genetic material (D)</p> Signup and view all the answers

What is the main function of DNA helicase in replication?

<p>To unwind the DNA double helix (D)</p> Signup and view all the answers

In transcription, what must occur during the initiation step?

<p>RNA polymerase binds to the promoter and unwinds the DNA (D)</p> Signup and view all the answers

What is the direction of RNA synthesis during elongation?

<p>5' to 3' (D)</p> Signup and view all the answers

Which of the following statements correctly describes the role of tRNA?

<p>tRNA delivers amino acids to the ribosome based on codon pairing. (D)</p> Signup and view all the answers

What is the main function of the 5' cap and the 3' poly A tail in RNA?

<p>They protect the RNA from degradation and assist in translation initiation. (A)</p> Signup and view all the answers

During translation termination, what occurs at the A site of the ribosome?

<p>Stop codon is recognized. (C)</p> Signup and view all the answers

What is the role of snRNPs in mRNA processing?

<p>To splice introns from the pre-mRNA. (C)</p> Signup and view all the answers

In prokaryotes, what are the sizes of the ribosomal subunits?

<p>30S and 50S (D)</p> Signup and view all the answers

How do eukaryotic mRNAs differ in terms of ribosomal binding sites compared to prokaryotic mRNAs?

<p>Eukaryotic mRNAs lack a ribosomal binding site. (A)</p> Signup and view all the answers

What binds to the aminoacyl site (A site) of the ribosome during elongation?

<p>Aminoacyl tRNA with an amino acid. (A)</p> Signup and view all the answers

What is the process in which plants use cold temperatures to promote flowering?

<p>Vernalization (B)</p> Signup and view all the answers

Which of the following refers to gene expression that is reversible and can be passed from cell to cell?

<p>Epigenetic gene regulation (B)</p> Signup and view all the answers

What term is used for the photographic representation of chromosomes?

<p>Karyotype (C)</p> Signup and view all the answers

During which phase of the cell cycle does the chromosome replicate?

<p>S phase (B)</p> Signup and view all the answers

What is the significance of crossing over during meiosis?

<p>It ensures genetic diversity. (C)</p> Signup and view all the answers

Which type of inheritance describes genes passed from the maternal parent in a non-Mendelian fashion?

<p>Cytoplasmic inheritance (D)</p> Signup and view all the answers

What does the term 'nonparental' refer to in genetics?

<p>Offspring with traits different from both parents. (B)</p> Signup and view all the answers

Which cellular process is disrupted by unregulated cell division?

<p>Mitosis (D)</p> Signup and view all the answers

What occurs during the G1 checkpoint of the cell cycle?

<p>Evaluation of environmental conditions (C)</p> Signup and view all the answers

What type of chromosomal inheritance is characterized by maternal inheritance only?

<p>Cytoplasmic (A)</p> Signup and view all the answers

What is the role of cyclin-dependent kinases (CDKs) in the cell cycle?

<p>They drive the progression of the cell cycle. (B)</p> Signup and view all the answers

What is the main outcome of meiosis II?

<p>Four haploid daughter cells (D)</p> Signup and view all the answers

What does the term 'linked genes' refer to in genetics?

<p>Genes that are inherited together due to close proximity on a chromosome. (B)</p> Signup and view all the answers

What is the primary structure of DNA made of?

<p>Nucleotides (B)</p> Signup and view all the answers

Flashcards

Photosynthesis

The process by which plants use sunlight, water, and carbon dioxide to produce their own food (sugars) and release oxygen.

Autotrophs

Organisms that can produce their own food, such as plants.

Chloroplasts

Organelles in plant cells where photosynthesis occurs.

Light Reactions

The first stage of photosynthesis, where light energy is captured and converted into chemical energy (ATP and NADPH).

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Dark Reactions

The second stage of photosynthesis, where the chemical energy (ATP and NADPH) from light reactions is used to convert carbon dioxide into sugars.

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Photorespiration

A process where rubisco binds to oxygen instead of carbon dioxide during photosynthesis. This is inefficient and occurs in hot, dry environments with low CO2 levels.

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C4 Plants

Plants that have adapted to hot environments by minimizing photorespiration. They use a specialized pathway to concentrate CO2 around rubisco, increasing efficiency.

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CAM Plants

Plants that open their stomata at night to absorb CO2 and store it in a special acid form. They release this CO2 during the day for photosynthesis.

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Mendel's Law of Segregation

During gamete formation, each parent contributes only one allele for each trait to their offspring. The alleles separate.

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Mendel's Law of Independent Assortment

Different traits are inherited independently of one another, meaning the inheritance of one trait does not influence the inheritance of another.

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Test Cross

A cross between an individual with a dominant phenotype (unknown genotype) and a homozygous recessive individual to determine the genotype of the dominant individual.

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Incomplete Dominance

A pattern of inheritance where the heterozygous phenotype is a blend of the two homozygous phenotypes.

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Codominance

A pattern of inheritance where both alleles are expressed equally in the heterozygote.

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Semiconservative Replication

A method of DNA replication where each new DNA molecule consists of one original strand and one newly synthesized strand.

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Bidirectional Replication

DNA replication proceeds in both directions from the origin of replication, forming two replication forks.

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Dispersive Replication

A hypothetical model of DNA replication where newly synthesized DNA fragments are interspersed with parental fragments, like shuffling a deck of cards.

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DNA polymerase proofreading

DNA polymerase has a built-in error-checking mechanism that allows it to identify and correct mistakes during DNA replication.

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Chargaff's Rule

The rule states that in a DNA molecule, the amount of Adenine (A) is always equal to the amount of Thymine (T), and the amount of Guanine (G) is always equal to the amount of Cytosine (C).

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Telomeres

Protective caps at the ends of chromosomes, consisting of short repetitive DNA sequences that prevent degradation.

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Leading Strand

The strand of DNA that is synthesized continuously during replication in the 5' to 3' direction, using a single RNA primer.

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Lagging Strand

The strand of DNA that is synthesized discontinuously during replication in the 3' to 5' direction, creating Okazaki fragments.

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Norm of Reaction

The range of phenotypes an organism can exhibit due to environmental influence.

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Gene Expression

The process by which genetic information encoded in DNA is translated into a functional protein.

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DNA Mutation

A permanent change in the DNA sequence that can alter gene expression and potentially affect phenotype.

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Gene Regulation

The process by which organisms control the expression of their genes in response to environmental cues.

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Epigenetic Gene Regulation

Alterations in gene expression that are not due to changes in DNA sequence but rather by modifications to DNA or its associated proteins.

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Vernalization

The process of promoting flowering in plants by exposing them to prolonged cold temperatures.

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Epigenetic Inheritance

The transmission of epigenetic modifications from one generation to the next.

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X Inactivation

In female mammals, one X chromosome is randomly inactivated in each somatic cell to equalize gene expression between males and females.

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Barr Body

The condensed, inactive X chromosome in female cells, visible under a microscope.

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Extranuclear Inheritance

The inheritance of genetic material located outside the nucleus, typically in organelles like mitochondria.

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Mitochondrial Inheritance

Mitochondria are inherited maternally, meaning only the mother can pass on mitochondrial DNA.

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Linked Genes

Genes located close together on the same chromosome, often inherited together.

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Recombination Frequency

The percentage of offspring that exhibit a different combination of alleles than their parents due to crossing over.

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Parental/Nonrecombinant Offspring

Offspring that inherit the same combination of alleles as their parents, indicating no crossing over occurred.

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Nonparental/Recombinant Offspring

Offspring that inherit a different combination of alleles than their parents, indicating crossing over occurred.

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Membrane Fluidity

The ability of a cell membrane to move and change shape. Fluidity is influenced by factors like the length of fatty acid tails, the presence of double bonds, and cholesterol levels.

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Passive Transport

Movement of molecules across a cell membrane without requiring cellular energy. Examples include simple diffusion and facilitated diffusion.

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Active Transport

Movement of molecules across a cell membrane against their concentration gradient, requiring energy, like ATP.

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Na+/K+ Pump

A primary active transport protein that pumps sodium ions out of the cell and potassium ions into the cell, both against their concentration gradients.

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Types of Transport Proteins

Transport proteins are membrane proteins that facilitate the movement of molecules across cell membranes. Two main types are channel proteins and transporter proteins.

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Transcription: Elongation

RNA polymerase moves along the DNA template strand in the 3' to 5' direction, synthesizing RNA in the 5' to 3' direction, using uracil (U) instead of thymine (T).

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Transcription: Termination

RNA polymerase reaches a terminator sequence on the DNA, causing it to detach from the template strand, ending transcription.

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mRNA Processing

Newly synthesized RNA undergoes modifications like adding a 5' cap and a 3' poly-A tail, providing stability and facilitating translation.

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Introns and Exons

Introns are non-coding sections of RNA that are removed during splicing, while exons contain coding sequences that are joined together to form mature mRNA.

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Genetic Code

The genetic code uses three-nucleotide codons to specify each amino acid, with 64 possible combinations.

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Translation: Initiation

The process begins with the formation of a complex between mRNA, tRNA carrying the start codon, and ribosomal subunits.

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Translation: Elongation

The ribosome moves along the mRNA in the 5' to 3' direction, adding amino acids to the polypeptide chain based on the codons.

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Translation: Termination

The ribosome encounters a stop codon on the mRNA, causing the polypeptide chain to be released and the ribosome to disassemble.

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Study Notes

Photosynthesis Summary

  • Photosynthesis is the process where cells use energy from the sun to turn solar energy into chemical energy (CO2 + H2O → Sugar + O2).
  • Autotrophs produce their own energy, phototrophs use solar energy, chemotrophs use chemical energy, and consumers/heterotrophs consume others for energy.
  • Photosynthesis includes light-dependent and light-independent reactions.
  • Light reactions convert light, CO2 to NADPH and ATP. Dark reactions use NADPH and ATP to produce carbohydrates and O2.
  • Pigments, like chlorophyll, capture light energy. Chlorophyll absorbs all colors except green which is reflected.
  • Chloroplasts are the site of energy production, composed of thylakoids (stacks called grana).
  • Chlorophylls a and b contain a porphyrin ring bound to magnesium. Carotenoids cause orange pigments.
  • Chlorophyll absorbs and captures light energy.
  • Absorption spectrum displays absorption versus wavelength; while Action spectrum shows photosynthesis versus wavelength.
  • Light reactions occur in the thylakoid membrane, using light energy.
  • The Z scheme involves two photosystems: Photosystem II (P680) oxidizes water, producing ATP. Photosystem I (P700) produces NADPH.
  • Dark reactions, also known as the Calvin cycle, take place in the stroma.
  • For every 6 CO2 molecules, 18 ATP and 12 NADPH are used, producing G3P (glyceraldehyde-3-phosphate).
  • Photorespiration occurs when rubisco adds oxygen to RuBP instead of CO2. This is common in hot, dry environments with limited CO2.
  • Different plants have adaptations to minimize photorespiration: C3 plants (e.g., wheat), C4 plants (e.g., corn), and CAM plants (e.g., cacti).

Mendelian Patterns of Inheritance Summary

  • Inheritance is the passing of traits from parents to offspring.
  • Pre-Mendelian Theories included the theory of acquired characteristics and blended inheritance.
  • Gregor Mendel's experiments with pea plants led to the discovery of inheritance patterns.
  • Mendel's laws:
    • Segregation: alleles separate during gamete formation.
    • Independent assortment: traits are passed on independently.
    • Separation: alleles are not linked.
  • Gene analysis includes tests crosses (homozygous recessive x dominant), two-factor crosses (using Punnett squares), and pedigree analysis (family traits).
  • Human chromosomes include autosomes and sex chromosomes (X and Y). X-linked traits appear more in males.
  • Wild-type alleles are common, while mutant alleles are rare.
  • Types of gene expression include incomplete dominance (intermediate traits), codominance (both traits expressed), and environmental roles (phenotype influenced by environment).

Eukaryotic Cell Cycle, Mitosis, and Meiosis Summary

  • Cell division is essential for growth and repair but can be harmful if unregulated.
  • Eukaryotes have a nucleus and organelles, while Prokaryotes do not.
  • Cytogenetics is the study of chromosomes.
  • Karyotype is a photographic representation of chromosomes.
  • Diploid cells have two chromosome sets, while haploid have one.
  • Homologous chromosomes (identical but different) are members of a chromosome pair.
  • The cell cycle stages (including interphase, G1, S, G2 and M phases).
  • Interphase (G1+S+G2), cell growth and chromosome replication.
  • Mitosis (PPMAT), division of the nucleus:
    • Prophase: chromosomes condense.
    • Prometaphase: spindle apparatus forms.
    • Metaphase: chromosomes align.
    • Anaphase: sister chromatids separate.
    • Telophase: chromosomes reach poles, nuclei reform.
  • Cytokinesis, cytoplasm divides into two daughter cells.
  • Meiosis (BAMSS) occurs in sex cell formation (sperm & egg):
    • Meiosis 1: separates homologous chromosomes.
    • Meiosis 2: separates sister chromatids.
  • Four haploid cells are produced from one diploid cell.
  • Bivalent: homologous chromosome pair associated.
  • Life cycles include diploid-dominant (most animals), haploid-dominant (many fungi), and alternation of generations (plants and some algae).

DNA Replication and Chromosomal Structure Summary

  • DNA is a double helix structure composed of base pairs.
  • DNA runs 5' to 3'
  • DNA replication:
    • Semiconservative: produces one molecule with one parental strand and one replicated strand.
    • Bidirectional: both parental strands stay as template but replicate fully
    • Dispersive: replicated DNA has fragments of replicated DNA
  • DNA polymerase ensures accuracy of replication.
  • Chargaff's rule describes equal amounts of base pairs.
  • Telomeres protect chromosome ends.
  • Avery, MacLeod, and McCarty's experiments showed DNA to be the genetic material.
  • DNA is stabilized by hydrogen bonds.
  • DNA polymerase replicates DNA.
  • Okazaki fragments are created during lagging strand replication.
  • DNA primase creates short RNA primers for DNA polymerase.
  • DNA ligase glues Okazaki fragments together.
  • Topoisomerases change DNA arrangement.
  • DNA can be synthesized from environmental DNA.

Membrane Structure, Synthesis, and Transport Summary

  • Cell membranes form the boundaries of cells.
  • Membranes are composed of phospholipid bilayers, proteins, carbohydrates.
  • Membrane fluidity is affected by factors like temperature, lipid composition (tail length), and cholesterol.
  • Membrane proteins (integral and peripheral), catalyze reactions, provide transport pathways, etc.
  • Selective permeability means membranes allow some molecules to pass but not others.
  • Transport methods include:
    • Passive transport (no energy):
      • Simple diffusion
      • Facilitated diffusion
    • Active transport (energy required):
      • Primary active transport
      • Secondary active transport
  • Membrane gradients, crucial for maintaining cell function.
  • Movement of water across membranes (isotonic, hypotonic, hypertonic)

Gene Expression at the Molecular Level Summary

  • The process of transforming genes into functional proteins.
  • Mutation is a heritable change in genetic material.
  • Genes are the blueprints for proteins.
  • Protein-coding genes direct the synthesis of mRNA.
  • Transcription (DNA to mRNA):
    • Initiation: RNA polymerase and promoter bind.
    • Elongation: RNA polymerase adds nucleotides to the growing mRNA strand.
    • Termination: RNA polymerase detaches upon reaching a terminator sequence.
  • mRNA processing (in eukaryotes) involves addition of a 5' cap and 3' poly-A tail, and splicing of exons and removal of introns.
  • Protein synthesis (translation, mRNA to protein):
    • Initiation: ribosome assembly on mRNA.
    • Elongation: tRNA brings amino acids to the ribosome.
    • Termination: release of the polypeptide chain.
  • Ribosomes, sites of protein synthesis.

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This quiz covers essential concepts in biology, focusing on photosynthesis and fundamental genetic principles. Explore questions about the processes of photosynthesis, the laws of inheritance, and key genetic terminology. Ideal for students studying these critical topics in biology.

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