Midtrimester

Question 1

What is the law of segregation ?

Answer 1

The two alleles for each gene separate during gamete formation.
The two alleles of each gene pair must segregate, that is, separate, into different gamete cells during the formation of eggs and sperm in the parents.

Question 2

In which ratio is a dominant trait presented?

Answer 2

3:1 ratio over the recessive trait in the F2 generation.

Question 3

How is it called a different version of the same gene?

Answer 3

allele

Question 4

What is the difference between genotype and phenotype?

Answer 4

The alleles found in an individual are called its genotype. An individual’s genotype has a profound effect on its phenotype.

Question 5

What will be the offspring of individuals of pure breeding?

Answer 5

Heterozygous, with an individual with the dominant phenotype.

Question 6

What will happen with an heterozygote cross?

Answer 6

genotype ratio of 1:2:1
Phenotype of 3:1

Question 7

Ratio of a dihybrid cross of nonlinked genes

Answer 7

Ratio phenotype 9:3:3:1
Genotype: R-Y-, R-yy, rrY-, rryy

Question 8

Law of independent assortment

Answer 8

Alleles of genes on non homologous chromosomes assort independently during gamete formation.

Question 9

The phenotype of a homozygote is the same as the phenotype of the heterozygote

Answer 9

Complete dominance
AA=Aa

Question 10

Incomplete dominance

Answer 10

snapdragons, 1:2:1 ratio and they present an intermediate phenotype (Aa)

Question 11

Co-dominance

Answer 11

Both alleles can be seen in the heterozygote

Question 12

Pleiotropy

Answer 12

When a gene has several phenotypic effects.

Question 13

Epistasis

Answer 13

a gene at one locus alters the phenotypic expression of a gene at a second locus.
in Labrador retrievers and many other mammals, coat colour depends on two genes

Question 14

quantitative characters

Answer 14

are those that vary in the population along a continuum.

Question 15

What does quantitative inheritance usually means ?

Answer 15

That there is polygenic inheritance. Polygenic inheritance h
Such as height or skin color, that is influenced by two or more genes. Because multiple genes are involved, polygenic traits do not follow the patterns of Mendelian inheritance

Question 16

Multifactorial

Answer 16

phenotype of a character depends on environment as well as genotype

Question 17

Test cross

Answer 17

Cross of a F1 with a recessive parental

Question 18

Backcross

Answer 18

Cross of a hybrid F1 with parent

Question 19

Monohybrid cross

Answer 19

Organisms that are heterozygous at one gene locus

Question 20

Dihybrid

Answer 20

An organism who is heterozygous at two gene loci AaBb

Question 21

How can the ratio in genes change?

Answer 21

Linked genes (on same chromosomes) – different ratios

Incomplete dominance – more classes

Epistasis (gene interaction) – less classes

Lethal types – less classes or reduced number

Question 22

What are some autosomal diseases?

Answer 22

Albinism
Cystic fibrosis
sickle cell

Question 23

What needs to happen for X- linked recessive to be expressed?

Answer 23

*Female needs to have two copies of the allele (homozygous recessive)
*A male only need to have one copy of the gene.

Question 24

X- linked recessive diseases

Answer 24

red-green colour blindness, Duchenne muscular dystrophy and haemophilia

Question 25

Dominantly inherited disorders

Answer 25

Some human disorders are caused by dominant alleles. Dominant alleles that cause a lethal disease are rare and arise by mutation At least one parent of the affected individual is affected.

Question 26

X inactivation

Answer 26

one of the two X chromosomes in each cell is randomly inactivated early in embryonic development. The inactive X condenses into an object called a Barr body.

Question 27

Which kind of genes do not assort independently ?

Answer 27

Linked genes do not assort independently as they are both in the same chromosome

Question 28

What happens with linked genes that have a recombinant frequency of nearly 50%?

Answer 28

Genes that are far apart on the same chromosome can have a recombination frequency near 50%. Such genes are physically linked, but genetically unlinked, and behave as if found on different chromosomes.

Question 29

abnormal number of chromosome/s

Answer 29

Aneuploidy

Question 30

= more than 2 complete chromosome sets eg, triploidy (3n), tetraploidy

Answer 30

Polyploidy

Question 31

more than 2 of a particular chromosome in diploid cells

Answer 31

Polysomy
Klinefelter syndrome is the result of an extra X chromosome in a male, producing XXY individuals. Results in a male phenotype, sometimes with certain female body characteristics.

Question 32

only one of a particular chromosome in diploid cells

Answer 32

Monosomy
Monosomy X, called Turner syndrome, produces XO females, who are sterile and may have other characteristic features

Question 33

three copies of a particular chromosome in diploid cells

Answer 33

Trisomy
Down syndrome
results from three copies of chromosome 21.

Question 34

Occurs when a chromosomal fragment is lost. The affected chromosome is then missing certain genes. (If the centromere is deleted, usually the entire chromosome will be lost.)

Answer 34

Deletion
The syndrome cri du chat (“cry of the cat”), results from a specific deletion in chromosome 5 ie. del 5p
A child born with this syndrome is mentally retarded and has a catlike cry; individuals usually die in infancy or early childhood.

Question 35

: The “deleted” fragment may become attached as an extra segment to a sister chromatid, producing a duplication. Alternatively, a detached fragment could attach to a nonsister chromatid of a homologous chromosome

Answer 35

Duplication

Question 36

A chromosomal fragment may also reattach to the original chromosome but in the reverse orientation

Answer 36

Inversion

Question 37

Moves a segment of a chromosome to another

Answer 37

Translocation

Question 38

Philadelphia chromosome

Answer 38

Translocation chr 922 is associated with chronic myelogenous leukemia

Question 39

What does hydroxyurea does?

Answer 39

Hydroxyurea blocks ribonucleotide reductase, the rate-limiting enzyme responsible for converting ribonucleotides to deoxyribonucleotide triphosphates (dNTPs). Deoxyribonucleotide triphosphates are needed for DNA synthesis.