Practice set 11

Question 1

What are homologous chromosomes?

Answer 1

Are 2 pieces of DNA that carry the same gene in a diploid organism ,one from each parent.

Question 2

What are the advantages and disadvantages of sexual versus asexual reproduction?

Answer 2

Sexual

Advantages

1) There is variation in the offspring
2) All individuals in the population are less likely to get diseases.
3) Through selective breeding can be to make natural selection faster and increase the production of food

Disadvantages

1) It takes time, and energy to find a mate
2) If an individual is isolated, cannot happen.

Asexual

Advantages

1) If conditions don’t change the population can increase a lot
2) Is faster than sexual reproduction
3) You only need 1 parent

Disadvantages

1) It doesn’t produces variation
2) All organism or indivuales can caught a disease because they are too similar or clones from.each other.
3) One species can only survive in one type of habitat.

Question 3

Define diploid and haploid. Will meiosis necessarily lead to formation of haploid gametes?

Answer 3

Haploid:Is a cell or nucleus that has a single set of chromosomes that are unpaired.

Diploid:Is a cell or nucleus containing 2 sets of chromosomes or homologous chromosome ,1 from each parent.The parents provide with 23 chromosomes each.

Yes, it will lead to haploid cells since it forms haploid cells from diploid.

To do this the zypotes go through 1 round of replication and 2 of division.

Question 4

Describe what happens during each stage of Meiosis(ask professor)

Answer 4

What happens is that the cell is focusing on cell growth,in the S-phase or second phase of interphase the cells copies or replicates the DNA of the chromosomes and in the G2 the cell undergoes the final preparations for meoisis.

Question 5

Meiosis involves 2 sets of cell division: 1 cell gives rise to 4 cells. You start with a cell with
46 chromosomes. How come after 2 cell divisions you end up with 23 chromosomes in each
cell?(ask professor)

Answer 5

We start with 2 cells with 46 pairs of duplicated chromosomes ,and after we go to the end of miosis the chromosomes separate.

Question 6

There is DNA replication before Meiosis I, but no DNA replication between Meiosis I and II.
Explain why.

Answer 6

The main purpose of miosis is to produce a haploid gamete,so there is not need of replication and grow in Meiosis 1 and 2,therefore there is no interphase

Question 7

What is synapsis? What is the synaptonemal complex?

Answer 7

1) Synapsis: Is the formation of a close association between homologous chromosomes in prophase 1.
2) Synaptonemal complex: Is a protein lattice that forms between homologous chromosomes during prophase I supporting crossing over.

Question 8

Describe the function of the recombination nodules

Answer 8

Protein gatherings that occur on the Synaptonemal complex that mark the points of crossing over events, and mediate the multistep process of genetic recombination between non sister chromatids.

Question 9

11. A certain female’s chromosomes 12 both have the blue allele for the wing color gene and
    chromosomes 19 both have the long allele for the antenna length gene. As cells in her ovaries
    undergo meiosis, her resulting eggs (ova) may have which of the following?(Ask professor)

Answer 9

a. Either two chromosomes 12 with blue alleles or two with orange alleles
b. Either two chromosomes 19 with long alleles or two with short alleles
c. Either one blue or one orange allele in addition to either one long or one short allele