Genetics 1

Question 1

genetics

Answer 1

the study of heredity and variation in organisms

Question 2

heredity

Answer 2

the passing on of characteristics from parent to offspring

Question 3

variation

Answer 3

the differences that exist within a species or population

Question 4

species

Answer 4

a group of organisms that can interbreed with each other and produce fertile offspring

Question 5

what does genetics attempt to explain

Answer 5

the similarities and differences between parents and offspring

Question 6

2 examples of variation in humans

Answer 6

eye colour, hair colour

Question 7

2 examples of variation in plants (roses)

Answer 7

different shape and colour of petals

Question 8

2 types of variation

Answer 8

inherited variations

acquired variations

Question 9

inherited variations

Answer 9

differences due to different genes that are passed from generation to generation eg. eye colour, blood type

Question 10

acquired variations

Answer 10

differences that arise during development and that are not passed on eg. accidental loss of limb

Question 11

where is information contains

Answer 11

in definite structures called genes

Question 12

where are genes located

Answer 12

on the chromosomes in the nucleus

Question 13

3 features of a chromosome

Answer 13

thread-like structures
composed of DNA and protein
carries genes

Question 14

number of chromosomes in the nuclei of an organism is usually

Answer 14

constant

Question 15

diploid

Answer 15

2n

2 sets of chromosomes

Question 16

haploid

Answer 16

n

1 set of chromosomes

Question 17

in diploid cells, how are chromosomes found?

Answer 17

in matching pairs; homologous chromosomes

Question 18

gene

Answer 18

unit of heredity \

Question 19

composition of a gene

Answer 19

DNA

Question 20

locus

Answer 20

position of a gene on a chromosome

Question 21

alleles

Answer 21

alternative forms of a gene occupying the same locus on a pair of homologous chromosomes

Question 22

what do alleles give rise to

Answer 22

variation in a species

Question 23

alleles in a diploid cell

Answer 23

2 alleles for every characteristic

Question 24

how many alleles are present in a gamete

Answer 24

1 (haploid)

Question 25

genotype

Answer 25

genetic make-up of an organism

consists of many sets of alleles

Question 26

phenotype

Answer 26

the visible expression of the genotype

depends on genotype and effect of environment

Question 27

which plant did mendel use

Answer 27

garden pea

Question 28

why did Mendel choose the garden pea (4 reasons)

Answer 28

• several pure breeding varieties available
• sharply contrasting and easily recognisable characteristics
• self-pollinating
• large numbers of offspring, easily

Question 29

monohybrid inheritance

Answer 29

the study of inheritance of one characteristic

Question 30

2 results from Mendel’s first cross

Answer 30

seeds collected from tall plants only produced tall plants and seeds collected from dwarf plants only produced dwarf plants

Question 31

what did mendel reason

Answer 31

that the dwarf characteristic which reappeared in the F2 generation must have been present in the F1 plants, but as it did not show he called it recessive

Question 32

Mendel’s first law

Answer 32

the law of segregation

Question 33

the law of segregation

Answer 33

characters are controlled by a pair of factors that separate during gamete formation. Only one factor of each pair is present in a gamete

Question 34

how to do a test cross

Answer 34

crossing the unknown genotype (TT) or (Tt) with the known homozygous recessive for this character (tt)

Question 35

test cross: 2 results

Answer 35

if all of the offspring show the dominant character, then the dominant parent is homozygous
if any of the offspring show the recessive character, the dominant parent is heterozygous

Question 36

incomplete dominance means

Answer 36

neither allele is expressed in the heterozygote

Question 37

homozygous genotype

Answer 37

identical alleles for a characteristic

Question 38

heterozygous genotype

Answer 38

different alleles for a characteristic

Question 39

dominant

Answer 39

an allele that is always expressed

Question 40

recessive

Answer 40

an allele that is only expressed when it is homozygous