Traits

Question 1

explain the role DNA plays in determining phenotype

Answer 1

An organism’s phenotype (physical traits and behaviours) are established by their inherited genes. Genes are certain segments of DNA that code for the production of proteins and determine distinct traits. Each gene is located on a chromosome and can exist in more than one form.20

Question 2

explain how mutations result in new alleles

Answer 2

The ultimate source of all genetic variation is mutation. Mutation is important as the first step of evolution because it creates a new DNA sequence for a particular gene, creating a new allele. Recombination also can create a new DNA sequence (a new allele) for a specific gene through intragenic recombination.

Question 3

some mutations can be passed onto offspring, others can not. explain why

Answer 3

Acquired mutations are not passed down if they occur in the somatic cells, meaning body cells other than sperm cells and egg cells. Some acquired mutations occur spontaneously and randomly in genes. Other mutations are caused by environmental factors, such as exposure to certain chemicals or radiation.

Question 4

explain dominant and recessive alleles

Answer 4

The most common interaction between alleles is a dominant/recessive relationship. An allele of a gene is said to be dominant when it effectively overrules the other (recessive) allele. Eye color and blood groups are both examples of dominant/recessive gene relationships

Question 5

define genotype

Answer 5

A person’s genotype is their unique sequence of DNA. More specifically, this term is used to refer to the two alleles a person has inherited for a particular gene. Phenotype is the detectable expression of this genotype – a patient’s clinical presentation.

Question 6

define homozygous

Answer 6

The presence of two identical alleles at a particular gene locus. A homozygous genotype may include two normal alleles or two alleles that have the same variant.

Question 7

define heterozygous

Answer 7

The presence of two different alleles at a particular gene locus. A heterozygous genotype may include one normal allele and one mutated allele or two different mutated alleles (compound heterozygote).

Question 8

explain how the genotype determines the phenotype

Answer 8

The term “phenotype” refers to the observable physical properties of an organism; these include the organism’s appearance, development, and behavior. An organism’s phenotype is determined by its genotype, which is the set of genes the organism carries, as well as by environmental influences upon these genes.