Chapter 14: Sticking Points and Moving Forward

Question 1

In Mendel’s experiments, name which generations were self-fertilizing and which generations were cross-fertilizing

Answer 1

The F1 generation(1st fillial generation) were cross fertilizing(between two true-breeding parents) to create hybrids

The F2 generation(2nd fillial generation) self-fertilized

This process showed at the time that one phenotypic trait showed over the other(like being dominant and recessive in genotype) in the F1 generation, and organisms can still carry genotypic traits that are not phenotypic traits until another generation occurs, like the F2 generation

Question 2

How do Mendel’s law of independent assortment connect to real life meaning in meiosis?

Answer 2

During meiosis, homologous pairs of chromosomes line up at the metaphase plate, and their orientation determines the way the alleles for different genes segregate. The orientation of each homologous pair is random, and there are two possible ways that each pair can align. This randomness during meiosis leads to independent assortment of the alleles for different genes, resulting in gametes with various combinations of alleles

Question 3

Be able to connect Mendel’s Laws to the exceptions!

Question 4

How does Mendel’s Principle of Segregation connect to real life meaning in meiosis?

Answer 4

the principle is that the physical basis for the segregation of Mendel’s traits is the separation of alleles, when homologous chromosomes pairs are separated in Meiosis I(separation of Pp to P and p)

An allele is connected to each chromosome, so when they are replicated and split, the alleles segregate with that chromosome

The process of synapsis connects to Mendel’s laws in meiosis:

Synapsis: bivalent formation(connection of 2 pairs of chromosomes), cross-over events between non-sister chromatids of the top of them

This connects to Mendel’s second law, independent assortment, where genes sort independently from each other during meiosis in synapsis

Question 5

4 Main Exceptions to Mendel’s principle of segregation

Answer 5

(Principle: two alleles (variants of a gene) for a trait segregate from each other such that each gamete carries only one allele for that trait).

• Incomplete dominance: both alleles for a trait are expressed in the heterozygous condition, creates intermediate phenotype(red+white = pink)
• Co-dominance: both traits expressed in heterozygous condition(ex: in IAIB blood type both antigens are expressed)

Question 6

Exceptions to Mendel’s Law of Independent assortment

Answer 6

Epistasis: In this case, the expression of one gene affects the expression of another gene. For example, in mice, the gene for coat color is affected by the gene for pigment production. If the pigment production gene is defective, then the coat color gene will not be expressed.

Linked Genes: In this case, two or more genes are located close together on the same chromosome, and they tend to be inherited together. This violates the principle of independent assortment, which states that alleles for different traits segregate independently of each other.

Environmental Effects: Sometimes, the environment can affect the expression of a gene, causing the trait to vary. This can cause the inheritance of the gene to appear non-Mendelian.

Genetic Imprinting: Some genes may be expressed differently depending on which parent they are inherited from. This means that the expression of the gene is dependent on the parental origin, violating the principle of independent assortment.(Kinda like sex-linked traits?)