Reproduction and inheritance

Question 1

What is the difference between asexual and sexual reproduction?

Answer 1

1. Asexual means just one parent. Identical genes so no variation between parent and offspring. 2. Sexual reproduction involves fusion of male and female gametes (sperm and egg) to produce genetically different offspring.

Question 2

What is mitosis?

Answer 2

When a cell reproduces itself, splitting into two cells with identical sets of chromosomes. Used for growth and repair as well as reproduction.

Question 3

What is meiosis?

Answer 3

Type of cell division in sexual reproduction. Creates cells whose chromosomes are not identical. Gametes are produced by meiosis

Question 4

What are chromosomes?

Answer 4

Found in cell nucleus, long lengths of DNA. Each human cell has 23 pairs of chromosomes (46 in total)

Question 5

What is structure of DNA?

Answer 5

Two strands coiled together in double helix. Held together by two pairs of bases: A-T (adenine and thymine) and G-C (guanine and cytosine)

Question 6

What are genes?

Answer 6

Short sections of DNA. Each gene is chemical instruction that controls inherited characteristics

Question 7

What are gametes?

Answer 7

Sperm cells and egg cells. Each has half number of chromosomes of normal cell: 23 (haploid)

Question 8

What happens at fertilisation?

Answer 8

Male gamete fuses with female gamete to form a zygote (fertilised egg). Zygote then divides (by mitosis) and develops into embryo

Question 9

What are male and female reproductive parts of flower?

Answer 9

1. Stamen is male part: anther produces pollen, filament supports anther
2. Carpel is female part: ovary contains eggs, stigma is part that pollen attaches to

Question 10

What is pollination?

Answer 10

Transfer of pollen from an anther to a stigma. Cross-pollination is transfer of pollen between different plants (= sexual reproduction)

Question 11

How can plants be adapted for insect pollination?

Answer 11

1. brightly coloured petals 2. scented flowers 3. sticky pollen grains 4. sticky stigma

Question 12

How can plants be adapted for wind pollination?

Answer 12

1. Lots of small, light pollen grains 2. Long filaments so anthers hang outside plant 3. Large, feathery stigma to catch blowing pollen

Question 13

How does fertilisation take place in plants?

Answer 13

1. Pollen lands on stigma 2. Tube grows from pollen grain to ovary 3. Nucleus from male gamete fuses with female gamete in ovary 4. Forms zygote –> divides to form embryo

Question 14

What is your genotype?

Answer 14

The alleles that you have eg Bb

Question 15

What is your phenotype?

Answer 15

The characteristics produced by your alleles eg brown hair

Question 16

What does ‘heterozygous’ mean?

Answer 16

One dominant gene, one recessive gene eg Bb, Rr

Question 17

What does ‘homozygous’ mean?

Answer 17

Both genes are the same eg BB, rr

Question 18

What is a dominant allele?

Answer 18

One which passes on the condition if just one of one of the genes is present eg if red eyes are dominant a mouse will have red eyes if they are RR or Rr

Question 19

What is a recessive allele?

Answer 19

The characteristic caused by the recessive allele only appears if both alleles are recessive eg if red eyes are recessive a mouse will only have red eyes if they are rr

Question 20

Give four effects of oestrogen in women during puberty

Answer 20

1. Hair grows (pubic and underarms) 2. Hips widen 3. Breasts develop 4. Periods start

Question 21

Give five effects of testosterone in men during puberty

Answer 21

1. Hair grows (face and body) 2. Muscles develop 3. Penis and testicles enlarge 4. Sperm production 5. Voice deepens