12.1 HY Fundamental Concepts of Genetics

Question 1

What are genes?

Answer 1

They are DNA sequences that code for heritable traits that can be passed from one generation to the next.

Question 2

What is an allele?

Answer 2

An alternative form of a gene. Like A, B, or O

Question 3

What are homologues?

Answer 3

They are two copies of each chromosome.
The exception to this are sex chromosomes, X & Y

Question 4

What is the locus?

Answer 4

The location of a gene on a specific chromosome.

Question 5

What is:
Complete Dominance?
Codominance?
Incomplete dominance?

Answer 5

Complete Dominance- one recessive and one dominant allele
Codominance- more than one dominant allele
Incomplete dominance- when a heterozygote expresses a phenotype that is intermediate between the two homozygous genotypes, such as when a pink flower is formed from a white and red flower mating.

Question 6

What is penetrance?

Answer 6

Is a population measure defined as the proportion of individuals in the population carrying the allele who actually express the phenotype.

AKA: the probability that a person with a particular genotype will express the phenotype.

Huntington’s Disease

Question 7

What is expressivity? Constant and variable?

Answer 7

Expressivity: varying phenotype despite constant genotype
Constant: all genotypes will express the same phenotype
Variable: individuals with the same genotype may ahve different phenotypes.

Neurofibromatosis Type II

Question 8

What are Mendel’s First Law (segregation)?

Answer 8

1. Genes exist in alternative forms.
2. An organism has two alleles for each gene
3. Two alleles segregate during meiosis
4. If two alleles are different, only one will be fully expressed.

In anaphase 1, homologous chromosomes are separated.