Genetic diversity

Question 1

Describe the steps in Meiosis 1.

Answer 1

• Interphase, paternal and maternal DNA replicates
• Prophase, nuclear membrane breaks down, chromosomes coil and condense and the centrioles move to poles. During prophase 1 crossing over can occur which is one cause of variation.
• Metaphase, homologous pairs line up on the equator of cell, random assortment can occur.
• Anaphase 1, Homologous pairs are seperated
• Telophase 1, nuclear memmbrane reforms
• Cytokinesis, cytoplasm splits and two haploid cells are formed

Question 2

Decribe the steps during meiosis 2.

Answer 2

-Prophase 2, nuclear membrane breaks down
- Metaphase 2, chromosomes line up in the equator of the cell snd spindle fibres attach to centromere
- Anaphase 2, Centromere divides and sister chromatids get pulled to either side of the cell by spindle fibres.
- Telophase 2, Nuclear membrane reforms
- Cytokinesis, cytoplasm splits and we are left with four haploid cells

Question 3

What is chromosome non - disfunction?

Answer 3

• Due to the non seperation of homologous pairs during anaphase 1 .
• Due to the non seperation of sister chromatids during anaphase 2 .

Question 4

Describe and explain the processes that occur during meiosis that increase genetic variation. (5)

Answer 4

• Homologous chromosomes pair up
• Random assortment/ INDEPENDENT SEGREGATION occurs
• Maternal and paternal chromosomes are re-shuffled in any combination
• Crossing over leads to the exchange of parts of non-sister chromatids/alleles between homologous chromosomes
• Both create a new combination of alleles

Question 5

What is the way to remember how to sentence an answer to do with natural selection?

Answer 5

Mutation
Variation
Advantageous Phenotype (decided by the selection pressure eg. predation)
Outcompete
Survive
Reproduce
Inherit (offspring inherit the allele)
Many generations (change to the allele frequency