2. Evolution Pt4

Question 1

If your sex chromosomes are XX what gender are you?

Answer 1

Female

Question 2

If your sex chromosomes are an X and a Y what gender are you?

Answer 2

Male

Question 3

What are chances of having a boy or girl?

Answer 3

50%

Question 4

Explain why probability of having a girl or a boy is 50%?

Answer 4

• the female egg will always produce an X chromosome

- but there’s a 50:50 chance of it being fertilised by a sperm with an X or Y chromosome

Question 5

What did Gregor Mendel discover?

Answer 5

• 19th century monk
• he cross-bred different peas and recorded the characteristics of there offspring (yellow, green, smooth, wrinkly)
• he concluded that packets of information could be passed from parent to offspring in predictable patterns

Question 6

Why did no one believe Gregor Mendel?

Answer 6

-at the time no one had seen a chromosome
And so didn’t understand his theory
-he didn’t publish his work so died before his work was recognised

Question 7

Define genotype

Define phenotype

Answer 7

• The combination of allele inherited from the parents

- the visible characteristics this produces

Question 8

Define dominate alleles

Answer 8

That you only need inherit one copy of that allele to be able to develop the characteristic

Question 9

What the genotype of a mouse with a black phenotype?

If black is the dominate allele

Answer 9

BB

Bb

Question 10

Define recessive alleles

Answer 10

You need to inherit two copies of the gene in order to develop the characteristic

Question 11

What would be the genotype of a mouse with a brown phenotype?
Brown being recessive

Answer 11

bb

Question 12

If both allele are the same the genotype is called…

Answer 12

Homozygous

Question 13

If both allele are diffrent the genotype is called…

Answer 13

Heterozygous

Question 14

What genetic diagram do you draw to work out the probability of inheriting a particular characteristic?

Answer 14

Punnett square

Question 15

Some ………… May be influenced by a number of different ………..

Answer 15

Characteristics

genes

Question 16

Define genetic disease

Answer 16

A diseases or disorder that can be passed on from parent to child

Question 17

What is cystic fibrosis?

Answer 17

• A disorder of cell membrane (caused by a recessive allele)

- That cause various organs to become clogged with a thick, sticky mucus

Question 18

Symptoms of cystic fibrosis?

Answer 18

• CF can damage the lungs, the pancreas and the reproductive system
• it causes repeated infections and can lead to death and infertility

Question 19

What allele would you needed to get cystic fibrosis?

Answer 19

-it’s caused by a recessive allele, so you need to have two copies of the gene

Question 20

What happens if you one dominate healthy allele and one with cystic fibrosis?

Answer 20

• you will have no symptoms but are a carrier

- 1 is 25 people in the UK are a carrier approx

Question 21

What treatments are there for cystic fibrosis?

Answer 21

• Physiotherapy to help clear the lungs of mucus
• antibiotics to treat the infections
• enzymes to replace the ones missing from the pancreas and to try and thin the mucus

Question 22

What is polydactyly?

Answer 22

When babies are born with extra digits (fingers or toes)

Question 23

How is polydactyly inherited?

Answer 23

Caused by a dominate allele

Question 24

Huntington is caused by a dominate allele. If a heterozygous mother has children with a healthy Homozygous father, what are the chances of their third child developing Huntington?

Answer 24

50%

Question 25

What is one future treatment that could cure a genetic recessive disease?

Answer 25

• it could be possible to insert a healthy copy of the gene into the necessary cells
• but for a dominate disease the unhealthy gene would have to be cut out of the DNA or silenced first

Question 26

Right now the best way to inform a prospective parent if they carry the diseased ………. Before having children is …….. ……….

Answer 26

• gene

- genetic screening

Question 27

What is embryo screening?

Answer 27

It can be used to test embryos for genetic diseases, either once a women is pregnant or part of the IVF process

Question 28

What 2 treatments are available for pregnant women as they can’t do embryo screening?

Answer 28

Amniocentesis

Chronic villus sampling

Question 29

Explain amniocentesis

Answer 29

• Collects amniotic fluid from around the foetus which will contain the baby’s cells
• they’re tested for the presence of diseased alleles

Question 30

Explain chronic villus sampling

Answer 30

Removes cells from the developing placenta which can be tested for diseased Alleles

Question 31

Advantages of screening

Answer 31

• reduces suffering as babies are born without the disease
• could eradicate a disease if everyone did it
• reduces financial cost on the parents/health service that treating the disease would involve

Question 32

Disadvantages if embryo screening?

Answer 32

• is expensive
• can produce false positive so healthy foetuses are terminated
• collecting cells from a foetus can damage it or lead to a miscarriage