Unit 10

Question 1

Draw a diagram to illustrate the formation of new allele combinations as a results of crossing over.
& Explain

Answer 1

see notion

Question 2

Contrast meiosis I with meiosis II.​

Answer 2

Meiosis I:

Reduction in chromosome number (diploid to haploid)

Chromosomes remain replicated with sister chromatids

Homologous chromosomes pair align, then separate into different daughter cells

Meiosis II:

No further reduction in chromosome number (haploid to haploid)

The sister chromatids of a replicated chromosome separate

No pairing of homologous chromosomes

Question 3

Describe random orientation and independent assortment.

Answer 3

During metaphase I of meiosis, the way the pairs of chromosomes align at the cell equator is random; this means that anaphase 1, either chromosome (maternal or paternal) can end up at either pole (and eventually either daughter cell).

Independent Assortment
Also, which way a pair is facing is independent (does not affect) of the way other homologous pairs are facing.

Question 4

Contrast discrete with continuous variation

Answer 4

Variation differences that exist between individuals can be described as:
-> discrete: individuals fall into a distinct category. There isn‘t a continuous range of variation, you either „are or are not“
-> continuous: there is a range of measurements from one extreme to the other. Continuous variation is often due to polygenics (combined effect of many genes) and is often affected by environmental influenced.

Question 5

Explain polygenic inheritance using an example of a two gene cross with codominant alleles

State example human characteristics that are associated with polygenic inheritance

Answer 5

Polygenic characteristics are those that are determined by many genes; for example skin color. Each gene has an additive effect on the overall phenotype.

height
-> skin color
-> eye color
-> weight
-> many personality traits
In fact, most traits are polygenic!

Question 6

explain polyploidy