Weekly Wrap Up 9: Cell Division, Mitosis, and Meiosis

What two things must be true for the double stranded structure of DNA to form?

1. The two strands of DNA must be oriented in the opposite direction

2. Both strands must be twisted into a helical shape

Where are nucleotides are always added to a DNA chain?

On the 3 prime carbon of the sugar

Which base is NOT used as part of the structure of DNA?

Uracil, it is used to replace the base T (thymine) in RNA

What is a minor groove?

The small gap between the strands of the spiral-shaped backbone

What is a major groove?

The large gap between the strands of the spiral-shaped backbone

What is pyrimidine in DNA structure?

Bases with a one-ringed molecular shape

• Cytosine (C)

• Thymine (T)

• Uracil (U)

What is purine in DNA structure?

Bases with a two-ringed molecular shape

• Adenine (A)

• Guanine (G)

What is the function of the bases in a DNA chain?

They are the "letters" used to store information in chromosomes

Are somatic cells and gametes diploid or haploid?

Somatic cells are diploid (contain two sets of chromosomes) and gametes are haploid (contain one set of chromosomes)

What does anisogamous mean?

An organism’s gametes differ in size and shape depending on the ‘gender’ of the gamete

What does one single germ cell produce at the end of meiosis?

4 haploid gametes

How do the chromosomes behave differently in prophase of meiosis I than they do in mitosis?

In meiosis, homologous chromosomes physically connect together to form a bivalent chromosome (a chromosome that has shared DNA with another chromosome)

How do the chromosomes behave differently in metaphase of meiosis I than they do in mitosis?

In meiosis, homologous chromosomes line up on random sides of the cell in a bivalent chromosome

What two things are bivalent chromosomes able to do that explains why meiosis produces gametes that are genetically unique?

1. DNA can be swapped between bivalent chromosomes by crossing-over

2. The random segregation of chromosomes in independent assortment makes unique sets of parental chromosomes