DNA , Genes And Chromosomes

Question 1

DNA is in what shape?

Answer 1

A double helix.

Question 2

How many cells does a normal human nucleus contain?

Answer 2

46 chromosomes or 23 pairs of chromosomes.

Question 3

The two strands of DNA are held together by chemicals called bases. What are the four bases ?

Answer 3

Adenine.
Cytosine.
Guanine.
Thymine.

Question 4

The bases of DNA are paired and they always pair in the same way, this is called?

Answer 4

Complementary base-pairing.

Question 5

What is asexual reproduction?

Answer 5

It involves only one parent. The offspring have identical genes to the parent and there is no variation.

Question 6

What is mitosis?

Answer 6

Is when a cell reproduces itself by splitting to form two cells with identical sets of chromosomes.

Question 7

Mitosis is not only for asexual reproduction, where else is it used?

Answer 7

It’s how all plant and animal cells grow and repair damaged tissues.

Question 8

What is sexual reproduction?

Answer 8

Involves the fusion of male and female gametes, there are two parents and the offspring contain and mixture of the parents genes.

Question 9

What is meiosis?

Answer 9

The production of four haploid cells whose chromosomes are NOT identical.

Question 10

Name something that reproduces asexually?

Answer 10

Bacteria.

Some plants.

Question 11

Label the male parts of a flower?

Answer 11

The stamen which contains -
The anther.
The filament.

Question 12

Label the female parts of a flower?

Answer 12

The carpel which contains -
The stigma.
The style.
The ovary.

Question 13

What is pollination?

Answer 13

It is the transfer of pollen from an anther to a stigma, so that the male gametes can fertilise the female gametes in sexual reproduction.

Question 14

What is cross pollination?

Answer 14

Is a type of sexual reproduction where pollen from an anther of one plant is transferred to the stigma of another.

Question 15

What things help plants cross pollinate?

Answer 15

Insects.

Wind.

Question 16

How are some plants adapted for insect pollination?

Answer 16

Brightly coloured petals.
Scented.
Big sticky pollen grains.

Question 17

How are some plants adapted for wind pollination ?

Answer 17

Small dull petals.
No scents.
Lots of pollen grains, small and light so the wind can carry them.
Long filaments.
Larger feathery stigma.

Question 18

What is fertilisation?

Answer 18

The fusion of gametes.

Question 19

Can flowering plants be fertilised by a different species of plant?

Answer 19

No.

Question 20

In the male reproductive system, sperm is mixed with a liquid called?

Answer 20

Semen.

Question 21

In the male reproductive system what is the scrotal sac?

Answer 21

The scrotum hangs behind the penis and contains the testes.

Question 22

In the male reproductive system what do the glands do?

Answer 22

Produce the liquid that is added to sperm to make semen.

Question 23

In the female reproductive system a ovum (egg) is produce every … Days?

Answer 23

28 days.

Question 24

In the female reproductive system what does the ovary do?

Answer 24

It is the organ that produces ova and sex hormones.

Question 25

In the female reproductive system what is the neck of the uterus called ?

Answer 25

Cervix.

Question 26

Secondary sexual characteristics of women?

Answer 26

Extra hair, pubic and underarms. Hips widen. Develops BOOBIES. Ovum release and start periods.

Question 27

Secondary sexual characteristics of men?

Answer 27

``` Extra hair on face and body. Muscles develop. Penis and testicles enlarge. Sperm production. Deepening of voice. ```

Question 28

What happens on day 1 of the menstrual cycle ?

Answer 28

The uterus lining breaks down for four days.

Question 29

In the menstrual cycle what happens day 4-14?

Answer 29

The uterus lining builds up again into a thick spongy layer full of blood vessels.

Question 30

At what day is the ovum released?

Answer 30

14th day.

Question 31

If brown eyes is dominant B and blue is recessive, and to heterozygous hamsters reproduce, what is the percentage of there offspring of having blue eyes?

Answer 31

25%

Question 32

What does homozygous mean?

Answer 32

This would mean you have two of the same alleles for that particular gene.

Question 33

What does heterozygous mean?

Answer 33

It means you have two different alleles for that particular gene.

Question 34

Your chromosomes control whether your male or female. The 23rd pair is labelled XX or XY. What is male and what is female?

Answer 34

XY is male. | XX is female.

Question 35

What are some variations in animals that are not effected by the environment?

Answer 35

Eye colour. Hair colour. Inherited disorders. Blood group.

Question 36

What is the theory of evolution?

Answer 36

Life began as simple organisms from which more complex organisms evolved.

Question 37

What is the simple definition of natural selection?

Answer 37

Survival of the fittest !

Question 38

Genetic variation is cause by...?

Answer 38

Sexual reproduction and mutations in the genes.