genetics

Question 1

allele

Answer 1

one alternative form of a given gene pair.

eg tall and short alleles for the height of pea plants.

Question 2

allelic pairs

Answer 2

a combination of two alleles

Question 3

genotype

Answer 3

the specific allelic combination for a certain gene or set of genes (Tt, TT, tt)

Question 4

phenotype

Answer 4

the appearance of a trait in an individual ( what it looks like tall or short)

Question 5

homozygous

Answer 5

an individual which contains two identical alleles ( DD, dd)

Question 6

heterozygous

Answer 6

an induviual that contains two diffrent alleles for an allelic pair ( Dd)

Question 7

testcross

Answer 7

the cross of any induviual to a homozygous recessive parent (to determine if the individual is homozygous dominant or heterozygous)

Question 8

monohybrid cross

Answer 8

a cross between parents with different single allelic pair(AA x dd)

Question 9

dihybrid cross

Answer 9

a cross between parents with different two allelic pairs (AaGg)

Question 10

Mendelian traits

Answer 10

traits that exist in one of two forms; no intermediate forms (widow’s peak or straight line)

Question 11

Continuous Traits

Answer 11

traits that exist in more than two forms; ( human height, skin colour, hair colour)

Question 12

law of unit character

Answer 12

traits are inherited or passed on from generation to the next by genes and these genes occur in pairs.

Question 13

law of dominance

Answer 13

one allele may mask the effect of the other.

Question 14

law of segregation

Answer 14

during meiosis alleles separate one gamete carries one and the other carries the other one

Question 15

law of independent assortment

Answer 15

two traits don’t depend on each other if a pea plant is yellow it doesn’t have to be round or wrinkled.

Question 16

incomplete dominance

Answer 16

this occurs when both alleles are expressed resulting in a blending of the alleles
ex. Red snapdragons, X White snapdragons resulting in pink snap dragons.

Question 17

codominance

Answer 17

this occurs when both alleles are expressed but not blended.

Ex. blood type AB in humans.

Question 18

X-linked genes

Answer 18

this gene is located on the X chromosome.

Question 19

multiple alleles

Answer 19

there are more than two possible alleles

Ex. four blood types

Question 20

polygenic inheritance

Answer 20

sometimes two or more genes affect a single characteristic.

ex. skin pigment is controlled by 3 genes at least

Question 21

sex-linked genes

Answer 21

a gene located on the sex chromosome is said to be sex-linked.

Question 22

crossing over

Answer 22

crossing over the process in which the genetic information between two non-sister chromatids during prophase 1 of meiosis.

Question 23

linkage map

Answer 23

a genetic map based on the frequency of recombination between genes due to crossing over

Question 24

nondisjunction

Answer 24

during meiosis, there is an error that prevents the sister chromatids to separate properly resulting in one gamete having two copies of the same chromosome and the other gamete receiving no copy.

Question 25

sex nondisjunction

Answer 25

nondisjunction of the sex chromosomes. when egg or sperm has an abnormal number of X or Y chromosomes. eg Klinefelter's XXY.

Question 26

aneuploidy

Answer 26

the condition of possessing an abnormal chromosome number.

Question 27

X-inactivation

Answer 27

in females, one of the x chromosomes becomes inactive forming a Barr body. females might have two types of cells.

Question 28

Nonnuclear Inheritance

Answer 28

not all eukaryotic cell's genes are located on nuclear chromosomes they are located on organelles. mitochondria and chloroplast contains DNA that carries a number of genes. for most plants and animals maternal inheritance is the rule for mitochondrial genes. most of the mitochondria is passed to the zygote from the cytoplasm of the egg the spem only contributes a haploid set of chromosomes. the egg also contributes that but it also contributes the cytoplasm and organelles. the genes of the mitochondria code for enzzymes that are involved in making ATP. ATP synthatse enzymes , protien complexes of the electron transport chain. mutations in mitochondrial dna reduce the amount of ATP and causees rare human disorders.