Simple inheritance in animals and plants

Question 1

For what two things is cell division necessary?

Answer 1

1) For the growth of an organism

2) The repair of damaged tissues

Question 2

What is mitosis? (in general terms)

Answer 2

Cell division that results in two identical cells being produced from the first one.

Question 3

What do chromosomes contain?

Answer 3

Genes (alleles) which must be passed on to each new cell.

Question 4

What er stem cells?

Answer 4

The cells at an early stage of animal and plant embryos, they are unspecialised.

Question 5

What is different about the differentiation of animal and plant cells?

Answer 5

Most animal cells differentiate at an early stage of an organisms development.
Plant cells can differentiate throughout the life of a plant as it continues to grow.

Question 6

Cells of offspring being produced by asexual reproduction are produced by which type of cell division?
What can be said about the alleles of the parents and offspring in asexual reproduction?

Answer 6

Cells of offspring being produced by asexual reproduction are produced by mitosis.
Offspring contain the same alleles as their parents.

Question 7

Detail the three main stages in mitosis.

Answer 7

1) The normal body cell has chromosomes arranged in 23 pairs.
2) As cell division starts, a copy of each chromosome is made.
3) The cell divides in two, to form two daughter cells, each daughter cell has a nucleus containing 23 pairs of chromosomes identical to the ones in the original parent cell.

Question 8

Cells in reproductive organs are produced by which type of cell division?

What are the gametes in humans?

Answer 8

Cells in reproductive organs are produced by meiosis.

The gametes in humans are the sperm and ova.

Question 9

Why does sexual reproduction result in variation?

Answer 9

Sexual reproduction results in variation as the gametes from each parent fuse. So half the genetic information comes from the father and half from the mother.

Question 10

When two gametes fuse, the fertilised egg cell divides repeatedly by which process of cell division?

Answer 10

Mitosis

Question 11

Detail the three main steps in Meiosis?

Answer 11

1) The chromosomes in the cell in the reproductive organs are copied.
2) The cell divides in two and these new cells immediately divide again.
3) This produces four gametes, each with a single set of chromosomes, each with a different combination of genes.

Question 12

What are stem cells and where are they found?

Answer 12

Stem cells are unspecialised cells found in the human embryo and adult bone marrow.

Question 13

What is differentiation?

Answer 13

Differentiation is when unspecialised stem cells develop into different types of body cell.

Question 14

What is special about cells in adult bone marrow?

Answer 14

The cells in adult bone marrow can change into other types of body cell, e.g. a blood cell.

Question 15

What do layers of cell in embryos differentiate into?

Answer 15

Layers of cells in embryos differentiate into all the cells the body needs.

Question 16

For what is it hoped human stem cells could be used for?

Answer 16

It is hoped that human stem cells can be made to differentiate into many type of cell to treat conditions such as paralysis, e.g. by differentiating into nerve cells.

Question 17

Who was Gregor Mendel?

Answer 17

Gregor Mendel was a monk who worked out how characteristics were inherited, he was the first person to suggest the idea of separately inherited factors.

Question 18

Why did it take a long time for Mendel’s ideas to be accepted?

Answer 18

It took a long time for Mendel’s ideas to be accepted because scientists did not know about chromosomes and genes until after Mendel died.

Question 19

What is DNA?

What are genes?

Answer 19

DNA is a very long molecule with a double helix structure.

Genes are short sections of DNA.

Question 20

Every individual has different DNA apart from which individuals?

Individuals unique DNA can be used to identify them by what?

Answer 20

Identical twins

Individuals’ unique DNA pattern can be used to identify them by their DNA fingerprint.

Question 21

What does each gene code for?

Answer 21

Each gene codes for a particular combination of amino acids which make a specific protein.

Question 22

Human beings have how may pairs of chromosomes?

What chromosomes do males and females have?

Answer 22

Human beings have 23 pairs of chromosomes.

Males have an X and Y chromosome (XY), females have two X chromosomes (XX).

Question 23

What are alleles?

Answer 23

An allele is a version of a particular gene.

Question 24

What is a dominant allele?

Answer 24

A dominant allele is one which will give an individual a certain characteristic even if they only inherit one of the alleles.

Question 25

What is a recessive allele?

Answer 25

A recessive allele is one which controls a characteristic that will be inherited by the offspring only if they inherit both alleles.

Question 26

What are genetic diagrams?

Answer 26

Genetic diagrams are models which can be constructed to predict and explain the inheritance of particular characteristics.

Question 27

What is a phenotype? What is a genotype?

Answer 27

The phenotype is the physical appearance of the inherited characteristic, e.g. dimples or no dimples. The genotype is the genetic make up/ alleles inherited, e.g. DD, Dd or dd.

Question 28

What does homozygous mean? What does heterozygous mean?

Answer 28

Homozygous means the alleles inherited are the same, homozygous recessive - dd or homozygous dominant DD. Heterozygous means the alleles inherited are different, Dd.

Question 29

If a genetic disorder is caused by a dominant allele, how many alleles does an individual have to inherit to have the genetic disorder? Give an example of a genetic disorder which is caused by a dominant allele.

Answer 29

If a genetic disorder is caused by a dominant allele a person only has to inherit one allele to have the disorder. Polydactyl, where a baby is born with extra fingers or toes.

Question 30

If a genetic disorder is caused by a recessive allele, how many alleles does an individual have to inherit to have the genetic disorder? Give an example of a genetic disorder which is caused by a recessive allele. What does this allele affect?

Answer 30

If a genetic disorder is caused by a recessive allele a person has to inherit two recessive alleles to have the disorder. Cystic fibrosis is caused by a recessive allele which affects cell membranes and causes the production of a thick sticky mucus. The mucus can affect several organs including the lungs and the pancreas.

Question 31

Parent who pass on a genetic disorder to their offspring but do not have the disorder themselves are called what?

Answer 31

Parent who pass on a genetic disorder to their offspring but do not have the disorder themselves are called carriers of the allele.

Question 32

How can genetic diagrams be useful in the inheritance of genetic disorders?

Answer 32

By using genetic diagrams it is possible to see how a genetic disorder has been inherited and to predict whether future offspring will inherit it.

Question 33

If a parents is heterozygous for polydactyl, what is the chance of each child inheriting the disorder?

Answer 33

If a parents is heterozygous for polydactyl each child has a 50% chance of inheriting the disorder.

Question 34

If both parents are heterozygous for cystic fibrosis, what is the chance of each child inheriting the disorder?

Answer 34

If both parents are heterozygous for cystic fibrosis each child has a 25% chance of inheriting the disorder.

Question 35

From which three sources may embryonic stem cells be taken?

Answer 35

1) Spare embryos from IVF 2) Created from adult cells 3) The umbilical cord of unborn babies.

Question 36

For what could embryonic stem cells be used? (2)

Answer 36

Embryonic stem cells may be used to grow new tissues and organs for transplant.

Question 37

Give three reasons why some people are concerned about the use of embryonic stem cells.

Answer 37

1) The embryos have the potential to be babies and are destroyed. 2) The embryo cannot give permission. 3) The research is expensive.

Question 38

What is embryo screening? | Why is this important?

Answer 38

Embryo screening involves tests to diagnose disorders before the baby is born. As it gives parents the choice of whether or not to terminate the pregnancy if their child will be born with a genetic disorder.

Question 39

What happens to embryos carrying faulty genes in IVF?

Answer 39

Embryos carrying faulty genes in IVF are destroyed.