B2.5 Simple inheritance in animals and plants

Question 1

Why do cells need to divide?

Answer 1

to replace lost cells (damaged or worn out) and make more cells for other purposes

Question 2

What is a gene?

Answer 2

a section of DNA that controls a characteristic or part of a characteristic, it contains instructions to make a specific protein

Question 3

What is an allele?

Answer 3

different forms of the same gene

Question 4

What are genes grouped together into?

Answer 4

chromosomes

Question 5

How many chromosomes does a human have in the nucleus of its body cells?

Answer 5

46 chromosomes in 23 pairs

one of each pair is from mother and one from father

Question 6

What is different about chromosomes in gametes?

Answer 6

sex cells contain only one of each pair of chromosomes

Question 7

What are the two types of cell division called?

Answer 7

Mitosis and Meiosis

Question 8

What is Mitosis?

Answer 8

asexual reproduction-produces two identical cells with same genetic info. no genetic variation
plants and animals use this for growth and repair
asexual reproduction also uses mitosis

Question 9

What is Meiosis?

Answer 9

produces gametes with one copy of each chromosome the gametes have 23 chromosomes each (humans)
meiosis halves the number of chromosomes before dividing and multiplying , it involves 2 divisions

Question 10

What does meiosis lead to?

Answer 10

the new cell will be a mixture of the two sets of chromosomes, this is how sexual reproduction produces genetic variation

Question 11

Define: dominant

Answer 11

an allele that is expressed even when in the presence of a recessive allele –> C

Question 12

Define: recessive

Answer 12

an allele that is only expressed when present with another recessive allele –> c

Question 13

What is the scientific name for: Aa

Answer 13

Heterozygous

Question 14

What is the scientific name for: AA

Answer 14

Homozygous

Question 15

Define: genotype

Answer 15

this describes the genetic makeup of an individual regarding a particular characteristic

Question 16

Define: phenotype

Answer 16

this describes the physical appearance of an individual regarding a particular characteristic eg. dimples / no dimples

Question 17

Advantages of genetic screening

Answer 17

• can check for genetic diseases
• prepare emotionally + financially
• select ‘healthy’ embryos (IVF)
• prepare for early medical intervention
• option of termination
• could save money in long term

Question 18

Disadvantages of genetic screening

Answer 18

• chance of miscarriage
• should not prevent a life from existing
• select features for ‘designer babies’
• could increase number of terminations

Question 19

What are stem cells?

Answer 19

unspecialised cells that can differentiate-can change into any type of cell
found in early human embryos and adult bone marrow
can be used to replace faulty cells

Question 20

Reasons against stem cell research

Answer 20

• human embryos shouldn’t be used since each is a potential life
• uncertainty, may not effectively sure all diseases
• can make arteries narrower, negative impact
• patients bodies might reject them
• morally wrong, if life begins at conception

Question 21

Reasons supporting stem cell research

Answer 21

• can drastically improve condition of many diseases
• helps to discover cures and treatments
• sickle cell anaemia, bone marrow transplant
• could make heart cells for heart disease or insulin producing cells for those with diabetes

Question 22

What is therapeutic cloning?

Answer 22

using cells from an adult to produce a cloned early embryo of themselves as a source of perfectly matched embryonic stem cells
could, in theory, be used to heal the original donor

Question 23

Who was Gregor Mendel and what was his contribution to modern genetics?

Answer 23

the first person to suggest separately inherited factors, which we now call genes
he noted how characteristics were passed on in generations of pea plants

Question 24

What causes cystic fibrosis and its symptoms?

Answer 24

a recessive allele
organs become clogged with thick, sticky mucus
you can be a carrier
treated by physiotherapy

Question 25

What is polydactyly?

Answer 25

babies born with extra fingers or toes

dominant allele

Question 26

What is Huntingdon’s chorea?

Answer 26

rare inherited disease
brain cells degenerate
dominant gene