revision

Question 1

homozygous

Answer 1

having two identical alleles of a particular gene or genes.

“homozygous embryos”

Question 2

heterozygous

Answer 2

having two different alleles of a particular gene or genes.

“the genetic study showed two heterozygous variants”

Question 3

dominant inheritance

Answer 3

Dominant inheritance means an abnormal gene from one parent can cause disease. This happens even when the matching gene from the other parent is normal. The abnormal gene dominates.

Question 4

recessive inheritance

Answer 4

Recessive inheritance means both genes in a pair must be abnormal to cause disease. People with only one defective gene in the pair are called carriers. These people are most often not affected with the condition.

Question 5

allele

Answer 5

each of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

Question 6

linked genes

Answer 6

When genes are close together on the same chromosome, they are said to be linked. That means the alleles, or gene versions, already together on one chromosome will be inherited as a unit more frequently than not.

Question 7

genotype

Answer 7

the genetic constitution of an individual organism.

Question 8

phenotype

Answer 8

the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Question 9

codominance

Answer 9

Codominance is a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele usually will be expressed, while the effect of the other allele, called recessive, is masked.

Question 10

incomplete/ partial/ imidiate dominace

Answer 10

An important subcase of dominance is immediate dominance. This is the case where the two nodes in question are connected by a single branch without any intervening nodes.

Question 11

modifier gene

Answer 11

Modifier genes are defined as genes that affect the phenotypic and/or molecular expression of other genes. Genetic modifiers can affect penetrance, dominance, expressivity, and pleiotropy (Nadeau, 2001).

Question 12

multiple alleles

Answer 12

Multiple alleles exist in a population when there are many variations of a gene present. In organisms with two copies of every gene, also known as diploid organisms, each organism has the ability to express two alleles at the same time. They can be the same allele, which is called a homozygous genotype.

Question 13

polygenic traits

Answer 13

A polygenic trait is one whose phenotype is influenced by more than one gene. Traits that display a continuous distribution, such as height or skin color, are polygenic.

Question 14

discrete v continuous variation

Answer 14

Discrete variation is either/or and is often caused by the presence or absence of a small number if genes. For example, our ability to “roll” our tongues is determined by just one gene. … This more complex cause brings about what is known as continuous variation. Height is a good example of continuous variation.

Question 15

x-linked traits

Answer 15

X-linked is a trait where a gene is located on the X chromosome. Humans and other mammals have two sex chromosomes, the X and the Y. In an X-linked or sex linked disease, it is usually males that are affected because they have a single copy of the X chromosome that carries the mutation.

Question 16

x-linked recessive traits

Answer 16

X-linked recessive inheritance refers to genetic conditions associated with mutations in genes on the X chromosome. A male carrying such a mutation will be affected, because he carries only one X chromosome. A female carrying a mutation in one gene, with a normal gene on the other X chromosome, is generally unaffected.

Question 17

x linked dominant traits

Answer 17

X-linked dominant inheritance is a way a genetic trait or condition can be passed down from parent to child through mutations (changes) in a gene on a single X chromosome. In females (who have two X chromosomes), a mutation in a gene on one of the X chromosomes is enough to cause the condition.

Question 18

y linked traits

Answer 18

A condition is considered Y-linked if the altered gene that causes the disorder is located on the Y chromosome, one of the two sex chromosomes in each of a male’s cells. Because only males have a Y chromosome, in Y-linked inheritance, a variant can only be passed from father to son.