DNA Biochemistry Quiz

DNA Biochemistry

Gene: A segment of DNA that codes for a specific protein or functional RNA molecule.
Allele: Alternative forms of a gene that occupy the same locus (position) on a chromosome.
Nucleic Acid: A type of biomolecule composed of nucleotides.
- 3 Parts of a Nucleotide:
  - Phosphate group
  - Pentose sugar (either ribose or deoxyribose)
  - Nitrogenous base (adenine, guanine, cytosine, thymine, or uracil)
- Function: Store and transmit genetic information.
DNA Molecule:
- Function: Carries the genetic instructions used in the development and functioning of all known living organisms.
- Parts:
  - Deoxyribose sugar
  - Phosphate group
  - Nitrogenous bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).
- Structure: Double helix, two strands running antiparallel, held together by hydrogen bonds between complementary base pairs.
  - Base Pairing: Adenine pairs with Thymine (A-T), Guanine pairs with Cytosine (G-C).
- DNA Replication:
  - Process: The DNA molecule unwinds and each strand serves as a template for the synthesis of a new complementary strand.
    - DNA polymerase is the enzyme that adds nucleotides to the new strand.
  - DNA Repair: Enzymes identify, remove, and replace incorrectly paired or damaged nucleotides.
RNA Molecule:
- Function: Carry genetic information from DNA to ribosomes for protein synthesis.
- Types: Messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA).
- Differences from DNA:
  - Sugar: Contains ribose sugar instead of deoxyribose.
  - Base: Contains uracil (U) instead of thymine (T).
  - Structure: Single-stranded, usually folded into a complex shape.

Central Dogma of Molecular Biology

Describes the flow of genetic information from DNA to RNA to protein.
Transcription: The process of copying DNA into RNA. Takes place in the nucleus.
- Molecules involved: RNA polymerase, DNA, mRNA.
Translation: The process of converting mRNA into a protein. Takes place in the cytoplasm at ribosomes.
- Molecules involved: mRNA, tRNA, ribosomes, amino acids.
Mutations: Permanent changes in the DNA sequence.
- Definition: Changes in the genetic code.
- Types:
  - Point mutations: Changes in a single nucleotide.
    - Frameshift mutations: Insertions or deletions that shift the reading frame of the genetic code.
      - Insertions: Adding an extra nucleotide.
      - Deletions: Removing a nucleotide.
    - Substitution mutations: Replace one nucleotide with another.
      - Silent mutations: Do not change the amino acid sequence of the protein.

Meiosis

Location:
- Males: Testes (gonads)
- Females: Ovaries (gonads)
Sex Cells:
- Males: Sperm
- Females: Egg (ovum)
Purpose: To produce gametes (sperm and egg) with half the number of chromosomes as the parent cell.
Haploid vs. Diploid:
- Haploid: Cells with one set of chromosomes (n).
- Diploid: Cells with two sets of chromosomes (2n).
Sister Chromatid: Identical copies of a chromosome that are attached at the centromere before cell division.
Homologous Pairs: Two chromosomes that have the same genes but different alleles.
Crossing Over: The exchange of genetic material between homologous chromosomes during prophase I of meiosis.
First Interphase: The cell grows and replicates its DNA.
Meiosis I:
- Prophase I: Chromosomes condense, homologous chromosomes pair up and exchange genetic material (crossing over), the nuclear envelope breaks down.
- Metaphase I: Homologous pairs line up at the metaphase plate, spindle fibers attach to the centromeres.
- Anaphase I: Homologous chromosomes separate and move to opposite poles of the cell.
- Telophase I: Chromosomes reach the poles, the cytoplasm divides, and two daughter cells are formed.
Interphase II: A brief interphase, no DNA replication occurs.
Meiosis II:
- Prophase II: Chromosomes condense, the nuclear envelope breaks down.
- Metaphase II: Sister chromatids line up at the metaphase plate, spindle fibers attach to the centromeres.
- Anaphase II: Sister chromatids separate and move to opposite poles of the cell.
- Telophase II: Chromosomes reach the poles, the cytoplasm divides, and four haploid daughter cells are formed.
Meiosis in Female Animals:
- Polar Bodies: Small, non-functional cells produced during oogenesis (egg formation).
- Asymmetrical cell division ensures that the egg receives most of the cytoplasm and organelles for proper development.

Sex and Development

Gonads: The organs that produce gametes.
Gametes: Sex cells (sperm and egg).
Male Reproductive Anatomy:
- Sperm Production Pathway:
  - Testes: Produce sperm.
  - Epididymis: Where sperm mature and are stored.
  - Vas deferens: Carries sperm from the epididymis to the urethra.
  - Seminal vesicles: Secrete a sugary fluid that provides energy for sperm.
  - Prostate gland: Secretes a milky fluid that neutralizes the acidity of the vagina.
  - Bulbourethral gland: Secretes a clear mucus that lubricates the urethra.
- Sperm Components:
  - Head: Contains the nucleus with DNA.
  - Midpiece: Contains mitochondria for energy production.
  - Tail: Allows for movement.
Female Reproductive Anatomy:
- Egg Production Pathway:
  - Ovaries: Produce eggs.
  - Fallopian tubes: Site of fertilization.
  - Uterus: Where the fertilized egg implants and develops.
  - Cervix: The opening of the uterus.
  - Vagina: The birth canal and the site of sperm deposition.
Fertilization: The fusion of sperm and egg to form a zygote.

Developmental Stages

Zygote: The fertilized egg.
Cleavage: Series of rapid cell divisions that increase the number of cells but not the overall size of the embryo.
- Formation of blastula/blastocyst: Hollow ball of cells.
  - Blastocyst: A stage of development where the embryo differentiates into the inner cell mass (ICM) and the outer trophoblast.
Gastrulation: Formation of the three germ layers:
- Ectoderm: Forms the skin, nervous system.
- Mesoderm: Forms muscles, bones, blood vessels.
- Endoderm: Forms digestive system, lungs.
Neurulation: Formation of the neural tube, which will develop into the central nervous system.
Notochord: A rod-shaped structure that supports the embryo and will later develop into the vertebral column.
Trimesters of Pregnancy:
- First Trimester (0-12 weeks): Organogenesis, significant growth, a period of high risk
- Second Trimester (13-27 weeks): Continued growth, some development.
- Third Trimester (28-40 weeks): Significant growth and development of the nervous system and lungs.
Childbirth:
- Stage 1: Dilation of the cervix (6-24 hours).
- Stage 2: Delivery of the baby (20 minutes to 2 hours).
- Stage 3: Delivery of the placenta (5 to 30 minutes).

Mendelian Genetics

Gene: A segment of DNA that codes for a specific protein or functional RNA molecule.
Allele: Alternative forms of a gene that occupy the same locus (position) on a chromosome.
Genotype: The genetic makeup of an individual.
Phenotype: The observable characteristics of an individual.
Homozygous: Having two identical alleles for a trait.
Heterozygous: Having two different alleles for a trait.
Dominant: An allele that masks the expression of the recessive allele.
Recessive: An allele that is only expressed when two copies are present.
Mendel's First Law (Law of Segregation): During gamete formation, the two alleles for a gene segregate so that each gamete receives only one allele.
Mendel's Second Law (Law of Independent Assortment): Alleles for different genes assort independently of one another during gamete formation.
Punnett Squares: A diagram used to predict the possible genotypes and phenotypes of offspring.
Incomplete Dominance: A heterozygous genotype results in a phenotype that is a blend of the two homozygous phenotypes.
Co-dominance: Both alleles for a trait are expressed in the heterozygous phenotype.
Pleiotropy: One gene influences multiple traits.
Polygenic Traits: Traits influenced by multiple genes.
Environmental Influence: The environment can influence the expression of genes.
Chromosomal Theory of Inheritance: Genes are located on chromosomes.
Chromosome vs. DNA vs. Gene:
- Chromosomes: Made up of DNA and proteins.
- DNA: The molecule that carries genetic information.
- Genes: Segments of DNA that code for specific traits.
Autosomes: The chromosomes that are not sex chromosomes.
Sex Chromosomes: The chromosomes that determine sex (X and Y in humans).