B5 INHERITANCE

Question 1

how are gametes made?

Answer 1

cell division called meiosis

Question 2

what does meiosis produce?

Answer 2

non-identical cells

Question 3

give an example on where meiosis takes place?

Answer 3

flowering plants

gametes = pollen and egg cells

Question 4

what is sexual reproduction and the features of it?

Answer 4

fusion of male and female gametes. (fertilisation).

mixing of genetic material

Question 5

what is an example of asexual reproduction?

Answer 5

aphid reproducing

Question 6

what is asexual reproduction?

Answer 6

only one parent.

only 1 parent of the offspring.

does not involve gametes = no mixing of genetic material = genetically identical = clones

Question 7

does meiosis take place in asexual reproduction?

Answer 7

no because it does not involve gametes

Question 8

does mitosis take place in asexual reproduction?

Answer 8

yes

Question 9

where does meiosis take place in the human body?

Answer 9

reproductive organs.
testes = male
ovaries = female

Question 10

1st stage of meiosis?

Answer 10

all of the chromosomes are copied

Question 11

2nd stage of meiosis?

Answer 11

cells divide into two

Question 12

3rd stage of meiosis?

Answer 12

divide one more time forming gametes

Question 13

what happens to the chromosomes in the gametes?

Answer 13

chromosomes are single , not paired .
(before they were in pairs)

meiosis has halved the number of chromosomes

Question 14

how many gametes does meiosis produce?

Answer 14

4 gametes from one original cell,
genetically different from each other.
each gamete has different alleles

Question 15

what happen to gametes after they are produced?

Answer 15

gamete from male and female join together (fertilisation).

after fertilisation the cell has normal number of chromosomes.

Question 16

what happens after fertilisation?

Answer 16

The new cell is divided by mitosis , producing clumps of identical cells = embryo.
as the embryo develops the cells differentiate forming different cell types

(in animal = nerve and muscle cells)

Question 17

what is DNA?

Answer 17

two polymer (lots of smaller molecules) strands that wrap around each other to form a double helix.

Question 18

where is DNA found?

Answer 18

chromosomes

Question 19

what is a gene?

Answer 19

small section of DNA on a chromosome , it encodes for a specific sequence for amino acids to make a specific protein

Question 20

how are proteins made?

Answer 20

joining together amino acids.

Question 21

how many genes does a human have?

Answer 21

thousands

Question 22

what is a genome?

Answer 22

entire genetic material of an organism

Question 23

what is the human genome?

Answer 23

entire genetic material that makes a human

Question 24

why is understanding the human genome important?

Answer 24

help us to search for genes that are linked to disease. e.g genes that increase the risk of developing cancer or Alzheimer’s disease.

help us understand and treat inherited disorders e.g cystic fibrosis.

trace human migration patterns from the past (helps people to discover their ancestry)

Question 25

where does each chromosome come from?

Answer 25

one from father
one from mother

Question 26

how many copies of genes do we have?

Answer 26

2 because chromosome comes in pairs

Question 27

what is an allele?

Answer 27

genes in different versions

Question 28

what does genotype tell us?

Answer 28

alleles present

Question 29

what does homozygous mean?

Answer 29

when a person has 2 copies of the same alleles

Question 30

what does phenotype tell us?

Answer 30

the characteristics caused by the person alleles

Question 31

what does heterozygous mean?

Answer 31

when a person has 2 different type of alleles

Question 32

what does a dominant allele show?

Answer 32

the phenotype even if there is only one copy present.

Question 33

what does a recessive allele show?

Answer 33

a recessive allele will only show in the phenotype if two copies are present (if no dominant allele is present)

Question 34

how are some characteristics controlled?

Answer 34

by a single gene

but most characteristics are the result of many genes acting together e.g height

Question 35

what is cystic fibrosis?

Answer 35

disorder of cell membranes

its controlled by a single gene
- has 2 alleles
- allele = normal cell membrane= dominant =
C
- allele = defective cell membrane = recessive = c

to have cystic fibrosis = person has to have two copies of defective allele (cc)

person with one defective allele and one normal allele does not have cf but thy are known as a carrier of cystic fibrosis allela

Question 36

what is polydactyly caused by?

Answer 36

dominant allele

person with normal allele + polydactyly allele = polydactyly (cannot be a carrier)

Question 37

what is polydactyly?

Answer 37

people have extra fingers or toes

Question 38

solutions for inherited disorders?

Answer 38

gene therapy
embryo screening

Question 39

what is embryo screening?

Answer 39

embryos are tested to see if they have the alleles for inherited disorders

embryos do not have defective alleles are implanted into the women = develop into healthy offspring

Question 40

issues with embryo screening?

Answer 40

expensive (some people think the money should be spent elsewhere in the health service)

A large number of embryos are created = small numbers are implanted = some healthy embryos are destroyed = people think its unethical

in the future, we may be able to screen embryos to produce offspring with desirable features , many people find this unethical

Question 41

gene therapy?

Answer 41

scientists may be able to correct faulty alleles and use this to treat inherited disorders

Question 42

what does a family tree only show?

Answer 42

only shows phenotype not genotype

Question 43

how many of the chromosome pairs determine the inherited characteristics only?

Answer 43

22

Question 44

males have the … chromosome

Answer 44

….= xy

Question 45

females have the…chromosome

Answer 45

….=xx