Reproduction and inheritance

Question 1

describe the differences between sexual and asexual reproduction

Answer 1

1) asexual involves mitosis
2) asexual creates identical offspring with no variation in the population
3) sexual involves meiosis
4) sexual creates genetically different offspring with variation in the population
5) sexual involves the fusion of male and female gametes

Question 2

what is fertilisation

Answer 2

the fusion of a male and female gamete to form a zygote (which undergoes cell division and develops into an embryo

Question 3

describe the structure of an insect pollinated plant

Answer 3

1) brightly coloured petals
2) scented flowers + nectaries
3) big sticky pollen grains
4) sticky stigma

Question 4

describe the structure of a wind pollinated plant

Answer 4

small dull petals
no nectaries
lots of light pollen grains
long filament that hangs outside the flower
large feathery stigma outside the flower

Question 5

describe the process leading to fruit formation

Answer 5

1) pollen grain lands on stigma
2) pollen tube grows out of the pollen grain and down through the style to the ovary and into the ovule
3) nucleus from the male gamete moves down the tube to join with a female gamete in the ovule
4) the nuclei fuse to make a zygote which divides by mitosis to form an embryo
5) the fertilised female gamete forms a seed and the ovary develops into a fruit around the seed

Question 6

how do germinating seeds utilise food reserves

Answer 6

when seeds are underground they cannot photosynthesise so they have a store of food reserves coated in a hard seed coat.
when the seed begins to germinate it uses the glucose from food stores to respire

Question 7

describe the natural methods of asexual reprosuction

Answer 7

1) runners: fast growing stems that grow sideways, just above the ground.
the runners take root at points in the ground and new plants grow there

Question 8

describe the artificial methods of asexual reprosuction

Answer 8

cuttings: cutting a bit off the parent plant and planting it

Question 9

structure of the male reproductive system

Answer 9

1) glands produce liquid to make semen
2) sperm duct carries sperm from testes to urethra
3) testes: produce sperm
4) urethra carries sperm through the penis
5) erectile tissue swells with blood

Question 10

describe the structure of the female reproductive system

Answer 10

1) ovaries : produce eggs and sex hormones
2) fallopian tubes: muscular tubes that carry ovum from the ovary to the uterus
3) uterus: where the embryo grows
4) uterus lining: good blood supply for the implantation of an embryo
5) cervix

Question 11

what is the role of the hormones in the menstrual cycle

Answer 11

1) FSH causes an egg to mature and stimulates oestrogen production
2) oestrogen inhibits FSH production and causes the lining of the uterus to thicken
3) LH stimulates the release of an egg
4) progesterone maintains the lining of the uterus and stops LH and FSH production

Question 12

describe the role of the placenta during pregnancy

Answer 12

lets the blood of the embryo and mother get very close to allow the exchange of food, oxygen and waste.

Question 13

what is the role of the amniotic fluid

Answer 13

to protect the baby from bumps.

the amnion membrane surrounds the baby and is full of amniotic fluid

Question 14

what is a genome

Answer 14

the entire DNA of an organism

Question 15

what is a gene

Answer 15

a section of a molecule of DNA that codes for a specific protein

Question 16

where are genes located

Answer 16

inside chromosomes in the nucleus

Question 17

describe a DNA molecule

Answer 17

2 strands coiled to form a double helix

Question 18

what are the strands of DNA linked by

Answer 18

a series of bases,
adenine + thymine
cytosine + guanine

Question 19

describe an RNA molecule

Answer 19

single strand; contains uracil instead of T

Question 20

describe transcription

Answer 20

1) RNA polymerase separates the DNA strands
2) the free RNA nucleotides form complimentary pairs with the bases along the template strand
3) RNA polymerase joins the nucleotides together to produce a sequence of mRNA
4) the mRNA leaves the nucleus and goes to the ribosomes

Question 21

describe the process of translation

Answer 21

1) the tRNA molecule has an anticodon which is complementary to a specific codon on the mRNA
2) the mRNA molecule enters the ribosome and each codon is matched with an anticodon
3) the ribosome joins the amino acids attached to the tRNA molecules and they form a chain of amino acids (ie a protein)

Question 22

what is an allele

Answer 22

an alternative form of a gene which give rise to different characteristics

Question 23

what is codominance

Answer 23

when neither allele is recessive so you show characteristics of both alleles

Question 24

when does mitosis occur

Answer 24

growth, repair, cloning, asexual reproduction

Question 25

define a mutation

Answer 25

a rare and random change in genetic material that can be inherited

Question 26

What is the diploid number of chromosomes in a human

Answer 26

46

Question 27

What is the haploid number of chromosomes in a human

Answer 27

23

Question 28

What increases the risk of mutations

Answer 28

exposure to ionising radiation (for example gamma rays, X-rays and ultraviolet rays) and some chemical mutagens (for example chemicals in tobacco

Question 29

describe the process of evolution by means of natural selection

Answer 29

Variation in a population (due to a mutation)
Limited resources cause competition for survival
Some varieties will have a better chance of survival
They have a better chance of breeding and passing on the allele
Greater proportion of the next generation will have the allele (and the characteristic)
They will outlive those without the allele

Question 30

why is cloning better than selective breeding

Answer 30

identical / no variation /
all have same characteristic/eq;
2. faster process / quicker process / eq;
4. no need for mating / no need for two parents /
no need to keep bull / no need to keep female /

Question 31

what is a codon

Answer 31

a sequence of three bases in the gene

Question 32

how many different possible codons are there

Answer 32

64 (4 different bases and 3 bases in each codon so 4 x 4 x 4)

Question 33

what do mutations do

Answer 33

change the sequence of DNA bases in a gene, sometimes changing the amino acid and protein it codes for.

Question 34

what increases risk of mutations

Answer 34

exposure to radiation

chemicals called mutagens