Mendelian Genetics

Question 1

What is the Law of Segregation?

Answer 1

It is when each organism has two “factors” for any given trait and these factors will separate during gametes formation. Meaning that each gamete contains only one factor for each trait.

Question 2

What is the Law of Independent Assortment?

Answer 2

When members of one pair of factors separate independently of members from another pair of factors so that all possible combination of factors can be in each gamete.

Question 3

Define Gene.

Answer 3

It is a segment of DNA on a chromosome that controls the expression of structural, physical, and even behavioral traits.

Question 4

Define Locus

Answer 4

the location of a particular gene on a chromosome. It will be the same on both homologus chromosomes.

Question 5

Define Alleles.

Answer 5

alternate or contrasting forms of a gene. Example: gene for flower color in peas has an allele that produces purple flowers and a contrasting allele that produces white flowers.

Question 6

What is a genotype?

Answer 6

the combination of the two alleles for a particular trait. Each one allele is contributed by each parent to the offspring during sexual reproduction.

Question 7

What is a homozygous genotype?

Answer 7

if the same allele is received from each parent.

Question 8

What is a heterozygous genotype?

Answer 8

if contrasting alleles are received from the parents.

Question 9

Define Phenotype

Answer 9

only one allele is usually expressed at anytime and the physical expression of the genotype.

Question 10

What is the dominant allele?

Answer 10

it is the allele that is expressed when two contrasting forms of a gene are present at the same time.

Question 11

What is the recessive allele?

Answer 11

the allele that is not expressed when two contrasting forms of a gene are present at the same time.

Question 12

Define Monohybrid Cross.

Answer 12

follows one pair of contrasting traits from pure-breeding parents through hybrid offspring (F1) to a third generation (F2)

Question 13

Define Monohybrid testcross.

Answer 13

uses a homozygous recessive individual to determine the genotype of an individual that displays the dominant phenotype.

Question 14

What happens if an individual is homozygous dominant?

Answer 14

all of the offspring display the dominant phenotype.

Question 15

What happens when an individual is heterozyous.

Answer 15

it is when half of the offspring display dominant phenotype and half display recessive phenotype.

Question 16

Define Dihybrid Cross.

Answer 16

follows 2 pairs of contrasting traits SIMULTANEOUSLY form pure-breeding parents (P) through hybrid offspring (F1) to a third generation (F2).

Question 17

Define incomplete dominance.

Answer 17

a situation where neighter allele may be completely dominant. Meaning the heterozygous genotype will produce an intermediate phenotype between the dominant and recessive phenotype.

Question 18

What is an example of an incomplete dominance?

Answer 18

a red flower may be incompletely dominant to a white flower with heterozygote producing a pink flower.

Question 19

What caused an incomplete dominace?

Answer 19

a dosage dominance.

Question 20

Define Codominance.

Answer 20

a situation where there are more than two alleles and then each allele may specify a particular substance that is expressed by the heterozygous genotype.

Question 21

What is a really good example of Codominance?

Answer 21

Human ABO blood type. Where Ia producing a protein A to make type A Phenotype. Ib produces a protein B to make type B phenotype, Ia and Ib are both present leading to be a type AB phenotype. and i does not specify a protein so it creates a type O phenotype.

Question 22

define Epistasis.

Answer 22

when genes at two different loci interact to control a single trait.

Question 23

Define pleiotrophy.

Answer 23

a situation in which a single gene affects more than one trait.

Question 24

What is an example of a pleiotrophy?

Answer 24

Albinism. Where an allele responsible for albinism also tends to cause crossed eyes.

Question 25

How many pairs of autosomes and sex chromosomes do humans have?

Answer 25

22 pairs of autosomes and one pair of sex chromosomes.

Question 26

Define Autosomes.

Answer 26

they are the same in both males and females and carry most of our genes.

Question 27

Define Sex chromosomes.

Answer 27

different in both males and femals and determine our sex. Genotype XX= produce female phenotype. Genotype XY= produce male phenotype.

Question 28

What is the definition of Human Sex Chromosomes?

Answer 28

they are not truly homologous because they Y chromosome is shorter than the x chromosome and is shaped differently.

Question 29

What is an X-linked gene?

Answer 29

any gene that is carried on non-homologous poriton of X chromosome.

Question 30

How many x-linked chromosomes do males have?

Answer 30

They have one copy of an X-linked chromosomes so they express whatever trait is controlled by the allele they have for that gene. Becuase of this a recessive allel cannot be masked because it is the only allele present. There is a 50% chance of exhibiting that trait.

Question 31

How many X-linked chromosomes do females have?

Answer 31

they carry two copies of the X-linked recessive allele and can only express a recexxive sex-linked trait.

Question 32

Who are heterozygous females?

Answer 32

They are called Carriers (GENOTYPE). and they express the dominate trait but possess one receswsive allele.

Question 33

How are sex-linked traits passed?

Answer 33

they are passed from father to son because the father can only contribute a Y chromosome to his son. They are only inherited by a daughter only if her father has the trait and her mother is at least a carrier.

Question 34

How are X-linked genes passed?

Answer 34

Through faather to daughter.