Reproduction and inheritance

Question 1

Where and what are chromosomes?

Answer 1

• found in the nucleus
• they are long lengths of DNA coiled up
• they contain your genetic material

Question 2

What is a gene?

Answer 2

• a short section of DNA

- each separate gene is a chemical instruction that codes for a particular protein

Question 3

What are human body cells and how many chromosomes are there in total in a nucleus?

Answer 3

• diploid=2 copies of each chromosome

- 46 chromosomes in total in a human cell

Question 4

What are the role of proteins in inheritance?

Answer 4

-control most processes in the body and determine inherited characteristics e.g eye colour

Question 5

What are alleles?

Answer 5

-different versions of the same gene

Question 6

What is asexual reproduction?

Answer 6

• only one parent

- the offspring have identical genes to the parent

Question 7

How does asexual reproduction work?

Answer 7

-Mitosis, an ordinary cell can make a new cell which is genetically identical by dividing in 2

Question 8

Examples of organisms which reproduce asexually.

Answer 8

• bacteria

- some plants

Question 9

Define mitosis.

Answer 9

-when a cell reproduces itself by splitting to form 2 cells with identical sets of chromosomes

Question 10

Explain the steps of mitosis.

Answer 10

• in a cell thats not dividing, the DNA is spread out in long strings
• it duplicates its DNA forming X shaped chromosomes
• the chromosomes line up in the centre of the cell and cell fibres pull them apart
• membranes form around each of the sets of chromosomes which become the nuclei of the 2 new cells
• the cytoplasm divides

Question 11

Define sexual reproduction.

Answer 11

• where genetic info from 2 organisms is combined to produce offspring which are genetically different to either parent
• the mother and father produces gametes (egg cell and sperm)

Question 12

What are gametes in terms of no. of chromosomes?

Answer 12

• haploid= half the no of chromosomes in a normal cell

- 23

Question 13

Fertilisation…

Answer 13

• a male gamete fuses with a female gamete to form a zygote which ends up with a full set of chromosomes
• the zygote undergoes cell division by mitosis and develops into an embryo
• the embryo inherits features from both parents

Question 14

What is meiosis?

Answer 14

• a type of cell division
• produces four haploid cells
• only happens in the reproductive organs

Question 15

Steps of meiosis.. (first division)

Answer 15

• duplicates its DNA
• the chromosomes line up in pairs in the centre of the cell, one chromosome in each pair came from mother and one from father
• the pairs are pulled apart = each new cell has one copy of each chromosome
• each new cell has a mixture of mother and fathers chromosomes

Question 16

Steps of meiosis.. (second division)

Answer 16

• the chromosomes line up again in centre of cell, the arms of the chromosomes are pulled apart
• you get four haploid gametes which have a single set of chromosomes

Question 17

What is the female reproductive part in plants?

Answer 17

-the Carpel

Question 18

What does the carpel consist of?

Answer 18

• ovary, stigma and the style
• stigma=end bit that pollen grains attach to
• style=rod like section that supports the stigma
• ovary=contains female gametes inside ovules

Question 19

What is the male reproductive part in plants?

Answer 19

-the Stamen

Question 20

What does the Stamen consist of?

Answer 20

• anther and the filament
• anther=contains pollen grains which produce male gametes
• filament= stalk that supports the anther

Question 21

What is pollination?

Answer 21

-transfer of pollen from an anther to a stigma so the male gametes cam fertilise the female gametes

Question 22

What is cross pollination?

Answer 22

• type of sexual reproduction where pollen is transferred from the anther of one plant to the stigma of another
• plants that cross pollinate rely on insects or wind

Question 23

How are some plants adapted for insect pollination?

Answer 23

• brightly coloured petals to attract insects
• scented flowers and nectaries to attract insects
• they make big sticky pollen grains which stick to insects as they go from plant to plant
• the stigma is sticky so pollen picked up by insects will stick to it

Question 24

How are some plants adapted for wind pollination?

Answer 24

• small dull petals on the flower
• no nectaries
• a lot of pollen grains- theyre small and light=carried by wind
• long filaments that hang the anthers outside the flower=lots of pollen gets blown away
• large, feathery stigma to catch pollen as its carried past the wind

Question 25

Steps of fertilisation in plants…

Answer 25

• pollen grain lands on stigma of a flower
• a pollen tube grows out of the pollen grain and down through the style to the ovary and into the ovule
• the two nuclei fuse together to make an zygote. Divides by mitosis to make an embryo
• each fertilised female gamete forms a seed, the ovary develops into a fruit around the seed

Question 26

What are the roles of runners?

Answer 26

• plants can reproduce asexually using runners
• the parent plant sends out runners-fast growing stems that grow out sideways, just above the ground
• the runners take root at various points and new plants start to grow
• the new plants are clones of the parent plant so there is no genetic variation

Question 27

What are the roles of cuttings?

Answer 27

• artificial method to clone plants
• garderners can take cuttings from good parent plants and then plant them to produce genetically identical copies of the parent plant
• these plants can be produced quickly and cheaply

Question 28

Define homozygous.

Answer 28

-you have 2 alleles the same for that particular gene e.g CC or cc

Question 29

Define heterozygous

Answer 29

-you have 2 different alleles fo that particular gene e.g Cc

Question 30

Environmental factors of genetic variation in humans.

Answer 30

• health

- sporting ability

Question 31

Environmental factors of genetic variation in plants

Answer 31

• sunlight
• temp
• mineral content