Module 1 - Cellular Reproduction and Chromosomal Inheritance

Question 1

What are the three components of a nucleotide?

Answer 1

A sugar molecule (ribose or deoxyribose), a phosphate molecule and a nitrogen-containing molecule (A, G, T, C, U)

Question 2

Prokaryotes divide by _____ _____, while eukaryotes divide by ______ or ______.

Answer 2

Binary fission, meiosis or mitosis.

Question 3

Describe the three stages of a mitotic cell cycle and their counterparts.

Answer 3

1. Interphase - duplication
   • G1 - cell growth, normal gene expression. ~10hr
   • S - copy DNA. ~9hr
   • G2 - cell growth, duplicate organelles. ~4hr
2. Mitosis (PPMAT) ~1hr
   • Prophase - chromosomes condense
   • Prometaphase - chromosomes attach
   • Metaphase - chromosomes align
   • Anaphase - chromosomes separate
   • Telophase - chromosomes relax
3. Cytokinesis - two new cells divide

Question 4

Describe the three stages of a meiotic cell cycle and their counterparts.

Answer 4

1. Interphase - duplication of chromosomes occurs producing a pair of duplicate chromosomes 2n = 2.
2. Meiosis I - separation of homologous chromosomes, produces two haploid daughter cells 2n = 2 -> n = 1.
   • Prophase I (chiasmata), Prometaphase I, Metaphase I, Anaphase I, Telophase I & Cytokinesis (no DNA replication, immediately followed by MII).
3. Meiosis II - separation of sister chromatids. Cells are haploid with chromosomes and there are four daughter cells produced (similar to mitosis).
   • Prophase II, Prometaphase II, Metaphase II, Anaphase II, Telophase II & Cytokinesis

Question 5

What are Mendel’s three principles?

Answer 5

1. Dominance - existence of dominant and recessive alleles.
2. Segregation - alleles segregate independently.
3. Independent assortment - alleles of different genes assort independently.

*Allele - same gene, different sequences, eg. allele for height is same but phenotypic heights differ.

Question 6

Describe incomplete and codominance.

Answer 6

Incomplete dominance occurs when the phenotype of a heterozygote is midway between the phenotype of two homozygotes, where one allele is partially or incompletely dominant over the other.
Codominance occurs when the heterozygotes expresses the phenotype of both homozygotes, when neither allele is dominant.

Question 7

Explain non-disjunction.

Answer 7

Non-disjunction is the failure of chromosomes to separate and segregate into daughter cells at division. Leads to chromosomal abnormalities eg. Klinefelter’s (XXY, XXXY, XXYY), Turner’s (XO) or Trisomy/Down Syndrome (XXX).