Biology Chapter: Cell Cycle and Mitosis

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Questions and Answers

Which nitrogenous base pairs with adenine in DNA?

Uracil

Thymine (correct)

Guanine

Cytosine

What is the role of helicase during DNA replication?

It removes introns from mRNA

It adds base pairs to the DNA strand

It binds Okazaki fragments together

It splits the DNA helix creating a replication fork (correct)

What is the primary difference between RNA and DNA?

RNA is composed of deoxyribose sugar and DNA contains ribose

RNA is double-stranded whereas DNA is single-stranded

RNA contains Thymine while DNA contains Uracil

RNA is a single helix and contains Uracil instead of Thymine (correct)

In the transcription process, which phase follows initiation?

Elongation Signup and view all the answers

Which of the following best describes Okazaki fragments?

Short sequences on the lagging strand of DNA Signup and view all the answers

What is the function of tRNA during the translation process?

To transfer amino acids to the ribosome Signup and view all the answers

Which enzyme is responsible for adding nucleotide base pairs in DNA's leading strand?

DNA polymerase Signup and view all the answers

Which step is NOT involved in the post-processing of mRNA before it leaves the nucleus?

Binding to ribosomes Signup and view all the answers

What occurs during prophase I that contributes to genetic variation?

Exchange of chromosome segments between non-sister homologous chromatids. Signup and view all the answers

During which phase do homologous chromosomes align along the equator?

Metaphase I Signup and view all the answers

How can the number of chromosomes in a sex cell be determined from a body cell of the same organism?

By dividing the number of body cell chromosomes by two Signup and view all the answers

What is the result of independent assortment during meiosis?

Each gamete receives a mixture of maternal and paternal chromosomes. Signup and view all the answers

What phase of the cell cycle does a cell spend the most time in?

Interphase Signup and view all the answers

What is nondisjunction?

A chromosome separation error. Signup and view all the answers

During which phase of mitosis do chromosomes align on the mitotic spindle?

Metaphase Signup and view all the answers

What is the primary outcome of meiosis as compared to mitosis?

Meiosis leads to four genetically unique haploid daughter cells Signup and view all the answers

How does nondisjunction during Anaphase I affect the daughter cells?

All daughter cells will have incorrect numbers of chromosomes. Signup and view all the answers

What was the phenotype ratio in the F1 generation of Mendel's pea plant crosses with purebred parents?

All plants were purple. Signup and view all the answers

What happens during Anaphase I of meiosis?

Homologous chromosomes are separated and pulled to opposite poles Signup and view all the answers

What is the function of the cleavage furrow during cytokinesis?

To separate the cell into two daughter cells Signup and view all the answers

What fundamental concept is demonstrated by crossing-over during prophase I?

Genetic variation Signup and view all the answers

What is a potential drawback to sexual reproduction?

Higher energy expenditure in creating offspring Signup and view all the answers

Which of the following is a result of independent assortment during meiosis?

Different combinations of alleles distributed to gametes. Signup and view all the answers

What is 'dinofuzz' associated with in fossils?

The fluff surrounding the dinosaur fossil Signup and view all the answers

What is the term for organisms that have identical alleles?

Homozygous Signup and view all the answers

Which of the following accurately describes a dominant allele?

It is always expressed over the recessive allele. Signup and view all the answers

How do genotype and phenotype differ?

Genotype is the genetic make-up, phenotype is the expression of those genes. Signup and view all the answers

What distinguishes codominance from incomplete dominance?

In codominance, both parent phenotypes are equally expressed. Signup and view all the answers

What is pleiotropy?

One gene controlling multiple traits. Signup and view all the answers

What outcome can be expected from a cross between a red flower and a white flower if incomplete dominance is observed?

Offspring will be pink. Signup and view all the answers

How can the genotype of potential offspring be determined?

Using a Punnett Square and the parents' genotypes. Signup and view all the answers

What primarily makes up a DNA molecule?

Nucleotides Signup and view all the answers

What is the function of a codon in a DNA or RNA molecule?

It codes for a specific amino acid. Signup and view all the answers

What type of mutation results in a premature stop codon?

Nonsense mutation Signup and view all the answers

How do silent mutations affect the resulting protein?

They have no effect on the protein. Signup and view all the answers

Where do transcription and translation occur in prokaryotic cells?

Cytoplasm Signup and view all the answers

What happens to lactase expression when lactose is absent in prokaryotes?

Lactase expression is silenced. Signup and view all the answers

Which type of mutation can lead to little or big changes in the protein structure?

Missense mutation Signup and view all the answers

What is the result of a substitution mutation in DNA?

Replacement of one nucleotide with another. Signup and view all the answers

How do cells become specialized despite having the same DNA?

Through regulation of gene expression. Signup and view all the answers

Study Notes

The Cell Cycle

90% of a cell's life is spent in interphase
Interphase is comprised of three phases:
- G1: gathering energy and proteins for DNA replication
- S: DNA replication occurs, resulting in two copies of the chromosomes
- G2: storing more energy and proteins, some organelles are duplicated

Mitosis

Prophase: nuclear membrane breaks down, mitotic spindle begins to form
Metaphase: chromosomes align on the mitotic spindle
Anaphase: sister chromatids separate and move to opposite poles
Telophase: nuclear membrane begins to form, a cleavage furrow develops

Cytokinesis

At the equator of the cell, a cleavage furrow pulls inward
Microfilaments force the cell membrane to contract and separate the cell into two daughter cells

Dinofuzz

"Dinofuzz" is the fluff that surrounded a dinosaur fossil (simple structure)
Sinosauropteryx likely used feathers for attracting mates or keeping warm

Sexual Reproduction

Sexual reproduction requires a lot of energy
Finding and attracting mates is an essential part of sexual reproduction
Forming haploid (sex) cells requires energy
Less offspring are produced in sexual reproduction compared to asexual reproduction

Meiosis

Meiosis results in four genetically unique haploid daughter cells for reproduction
Meiosis reduces the number of chromosomes by half
Mitosis results in two genetically similar diploid daughter cells for growth and repair
Mitosis maintains the number of chromosomes

Meiosis I

Prophase I: membrane around the nucleus breaks down, spindle fibers begin to form
Crossing-over: exchange of chromosome segments between non-sister homologous chromatids
Metaphase I: the meiotic spindle is fully formed, pairs of homologous chromosomes align along the "equator," chromosomes attach to spindle tracks to prepare for separation
Independent Assortment: many arrangements of homologous chromosomes during Metaphase I, different combinations of chromosomes in the final daughter cells
Anaphase I: homologous chromosomes are pulled away from the equator, sister chromatids stay together
Telophase I: chromosomes reach the poles, the nuclear membrane forms
Cytokinesis: two daughter cells form

Meiosis II

Sister chromatids separate

Genetic Variation During Meiosis

Crossing over occurs after Prophase I
Independent Assortment occurs after Metaphase I

Nondisjunction

Error in chromosome distribution during Anaphase I or Anaphase II
In Anaphase I: chromosome pairs fail to separate, all daughter cells have the incorrect number of chromosomes
In Anaphase II: sister chromatids fail to separate, some daughter cells have the incorrect number of chromosomes

Patterns of Inheritance

Mendel observed traits such as pea color and plant height in his experiments
Hybrids are the result of two parents that differ in a given trait
In the F1 generation of a cross between purebred purple and white flowers, all flowers are purple, not blended colors
F2 generation shows a 3:1 ratio of purple to white flowers, regardless of which parent was purple
Alleles are versions of genes
Homozygous: identical alleles
Heterozygous: different alleles
Dominant alleles are expressed in a hybrid, while recessive alleles have no noticeable effect

Genotype vs. Phenotype

Genotype is the genetic makeup of an individual
Phenotype is the outward expression of those genes

Punnett Squares

Punnett squares can be used to determine the possible genotypes of offspring from two parents with known genotypes

Chickenosaurus

Jack Horner proposed that a small "pet dinosaur" could be created by manipulating the genes of a chicken embryo and reversing evolution to bring dinosaur-like features

Variations on Dominance

Incomplete dominance: heterozygotes appear as a mix between parent appearances
Codominance: both parent alleles are expressed in the phenotype of the offspring

Pleiotropy

One gene that affects many traits
Sickle cell anemia can lead to:
- Affects the hemoglobin protein and RBC shape
- Retinal detachment, liver enlargement, renal failure, stroke, heart attack

Structure of DNA

Double helix composed of nucleotides
Nucleotides are composed of: nitrogen base, phosphate group, and deoxyribose sugar
Bases form pairs between one purine (adenine, guanine) and one pyrimidine (thymine, cytosine)

DNA Replication

Helicase splits the helix, forming a replication fork
DNA polymerase adds base pairs to the 3' end of the leading strand, and in sections to the lagging strand
DNA ligase binds Okazaki fragments together
The end result of DNA replication is two new DNA strands that are exact copies of the original

RNA

RNA is a single helix
Uracil replaces thymine in RNA

Transcription

Initiation: RNA polymerase binds to the promoter region of the gene
Elongation: RNA polymerase moves along the DNA, adding RNA nucleotides
Termination: RNA polymerase reaches the termination sequence and detaches

mRNA Processing

In eukaryotes, mRNA undergoes post-processing before it is ready for translation
Stabilizing proteins are added to prevent degradation
Caps are added to the ends of mRNA
Introns are removed
Exons remain

Translation

The process of building proteins from mRNA
Ribosomes and mRNA are involved
tRNA interacts with the start codon to begin translation

Mutations

A codon is a sequence of three consecutive nucleotides in a DNA or RNA molecule that codes for a specific amino acid
Mutations are permanent changes in the genetic information of a cell or virus
Substitutions: replacement of one nucleotide base for another
Silent mutation: codon for the same amino acid
Missense mutation: codon for different amino acid
Nonsense mutation: stop codon, resulting in a prematurely ended protein

Gene Control

Cells containing the same DNA become specialized by regulating gene expression
Gene expression is regulated by activating and deactivating genes
Proteins are created at specific times

Gene Regulation in Prokaryotes

Transcription and translation occur in the same location (cytoplasm) almost simultaneously in prokaryotes
Prokaryotes control gene expression by regulating the transcription step
Example: lactose and lactase
Operon: related genes and sequences, such as lac operon

How Prokaryotes Regulate Gene Expression

Prokaryotes regulate gene expression by regulating the transcription step

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Description

Explore the intricacies of the cell cycle, including interphase and mitosis, where cellular division prepares for reproduction. Learn about the steps of cytokinesis and the unique concept of 'Dinofuzz' found in dinosaur fossils. This quiz will test your knowledge on these fundamental biological processes.