Inheritance

Question 1

Why does sexual reproduction bring about variation?

Answer 1

Gametes produced by meiosis in sex organs of parents. This introduces variety, as each gamete is different. Then when the gametes fuse, one of each pair of chromosomes comes from the parents

Question 2

Why is there no variation in asexual reproduction?

Answer 2

The offspring are produced as a result of mitosis from the parent cells, so they contain exactly the same chromosomes and the same genes as parents. No variation in genetic material.

Question 3

What are stem cells?

Answer 3

Undifferentiated cells which can develop into different types of cells depending on the instruction that is given.

Question 4

What is differentiation?

Answer 4

Differentiation is the process by which a cell changes to become specialised for its job.

Question 5

What are the advantages and disadvantages of stem cells?

Answer 5

Advantages:

embryonic stem cells offer one of the best chances we have for finding treatments such as paralysis.

The embryos used are generally spare embryos from fertility treatment, they would be destroyed anyway.

Embryonic stem cells could be used to grow new tissues and organs for organ transplants.

Curing patients that already exist is more important than embryo rights.

Disadvantages: all embryos have the potential to become babies, therefore it would be wrong to experiment on them and destroy them.

Embryos cannot give consent, it is unethical

It is taking a long time go develop and and money could be better spent on other things.

Question 6

What is a gene?

Answer 6

A gene is a small section of DNA that controls characteristics. Each gene codes for specific sequence of amino acids, which make a specific protein.

Question 7

What is therapeutic cloning?

Answer 7

Cloning biological material to produce embryos from which stem cells can be taken and used in research to find treatment for a range of diseases

Question 8

What are the function of chromosomes?

Answer 8

Carry our genetic information.

Question 9

Why are sex chromosomes special?

Answer 9

Females-XX chromosomes

Male-XY chromosomes

Question 10

What are dominant alleles?

Answer 10

Alleles that control the development of a characteristic even when they are present in only one of your chromosomes

Question 11

What is meant by homozygous ?

Answer 11

An individual with 2 identical alleles( DD, dd)

Question 12

What is meant by heterozygous?

Answer 12

An individual with different alleles( Dd),

Question 13

What is genotype and phenotype?

Answer 13

Genotype describes the genetic composition of an individual regarding a specific characteristic.

Phenotype describes the appearance of an individual, regarding a specific characteristic.

Question 14

What is polydactyl?

Answer 14

This is a genetic disorder that results in an individual having extra fingers or toes, caused by dominant allele.

Question 15

What is cystic fibrosis?

Answer 15

Genetic disorder in which a thick, sticky mucus is made that affects many organs in your body, e.g lungs and your digestive system. It can clog your airways and cause breathing problems.

If is caused by recessive allele, so it must be inherited from both parents.
A lot of people are carriers but have no idea, so child can inherit even if the parents don’t have themselves.

Question 16

What are chromosomes made off?

Answer 16

Long molecules of a chemical known as DNA. This has a double helix structure

Question 17

What is genetic fingerprinting?

Answer 17

Each person has unique DNA, this can be identified in genetic fingerprinting.

Question 18

What is recessive?

Answer 18

An allele that controls the development of a characteristic only if the dominant allele is not present.

Question 19

What is genetic screening?

Answer 19

Screening for alleles that cause genetic disorders.

Question 20

Advantages and disadvantages of genetic screening

Answer 20

Reduces the amount of people with genetic diseases in the population
Treating disorders cost taxpayers money
Can prevent series of diseases in family line

It is expensive, can cause miscarriage and can cause ‘designer babies’

Question 21

What is the difference between plant and animal differentiation?

Answer 21

Most animal cells differentiate at an early stage in life but plants maintain the ability to differentiate throughout their lives. In mature animals, cell division is restricted to cell replacement and repair.

Question 22

What is mitosis?

Answer 22

When a cell reproduces itself by splitting to form two identical offspring.

In a cell not dividing, DNA is all spread out in long strings.

1) When cell gets signal gets signal to divide it duplicates its DNA. The DNA is copied forms X shaped chromosomes. Each ‘arm’ of the chromosome is an exact copy of the other.
2) The chromosomes then line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell
3) Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells.
4) Lastly, the cytoplasm divides.
5) You have two cells containing the same DNA! They’re identical.

Question 23

What is meiosis?

Answer 23

Meiosis produces cells which have half the number of chromosomes. You get four gametes with only a single set of chromosomes in it.

Before cell starts to divide, it duplicates its DNA- one arm of each chromosome is an exact copy of the other arm.

In the first division, the chromosome pairs line up in the centre of the cell.

The pairs are then pulled apart, do each new cell only has one copy of each chromosome. Some of the father’s and some of the mother’s chromosome go into each cell.

Each cell will have a mixture of mother’s and father’s chromosomes. This creates variation.

In the second division the chromosomes line up again in the centre of the cell. The arms of the chromosomes are pulled apart.

Get 4 gametes with a single set of chromosomes in. After gametes join at fertilisation, the cell grows by repeatedly dividing by mitosis.