Inheritance

Question 1

what is sexual reproduction? (3)

Answer 1

• the fusion of male and female gametes
• the offspring receives genetic information from both the male and female parents
• every gamete is different, which means there’s variation in the offspring

Question 2

what is asexual reproduction? (3)

Answer 2

• only one parent is involved so there’s no fusion of gametes and no mixing of genetic information
• all offspring are genetically identical because all the gametes are the same
• only involves mitosis

Question 3

where does meiosis take place?

Answer 3

in the reproductive organs

Question 4

what is the meiosis process? (3)

Answer 4

1. dna replication
   - the cell duplicates its genetic information, forming ‘two-armed’ chromosomes
   - each ‘arm’ is an exact copy of the other
   -after replication the chromosomes arrange themselves into pairs
2. first division
   - the chromosomes line up in the centre of the cell
   - they are then pulled apart so each new cell has only one copy of each chromosome
3. second division
   - chromosomes line up again in the centre of the cell, where the two ‘arms’ are pulled apart

Question 5

what is the end product of meiosis?

Answer 5

four non-identical daughter cells are produced and the chromosomes in these cells are now single - at the beginning, they were in pairs

Question 6

what happens after fertilisation?

Answer 6

the new cell divides by mitosis, producing a clump of identical cells (an embryo)

Question 7

what is DNA? (3)

Answer 7

• contained within chromosomes
• determines our inherited features
• consists of two strands

Question 8

what is the name of the structure of DNA?

Answer 8

double-helix structure

Question 9

define gene

Answer 9

a small section of DNA on a chromosome

Question 10

what does each gene do?

Answer 10

encodes for a specific sequence of amino acids to make a specific protein

Question 11

define genome

Answer 11

the entire genetic material of an organism

Question 12

define human genome

Answer 12

the entire genetic material that makes a human

Question 13

what are the benefits of scientists studying the entire human genome? (3)

Answer 13

• helps us to search for genes that are linked to certain diseases
• helps us to understand and treat inherited disorders
• can use the human genome to trace human migration patterns

Question 14

define allele

Answer 14

versions of a gene

Question 15

define genotype

Answer 15

tells us the allele’s present

Question 16

define phenotype

Answer 16

tells us the characteristics/features of a person based on their alleles

Question 17

define homozygous

Answer 17

a person that has two copies of the same allele

Question 18

define heterozygous

Answer 18

a person that has two different allele’s

Question 19

in which case would a recessive allele be shown in the phenotype of a person?

Answer 19

if there’s two of them (ee, ff, cc)

Question 20

what is cystic fibrosis

Answer 20

a disorder of cell membranes

Question 21

which allele’s must a person have in order to have cystic fibrosis?

Answer 21

two copies of the defective cell membrane allele (cc)

Question 22

which allele’s must a person have to count as a carrier of cystic fibrosis?

Answer 22

one defective allele and one normal allele (Cc)

Question 23

what is polydactyly

Answer 23

extra fingers or toes

Question 24

what is polydactyly caused by?

Answer 24

a dominant allele

Question 25

define embryo screening

Answer 25

in which an embryo is tested to see if they have the allele’s for inherited disorders

Question 26

what is the advantage and disadvantages (2) of embryo screening?

Answer 26

ADVANTAGE
scientists may be able to correct faulty allele’s and use this to treat inherited disorders

DISADVANTAGES

expensive - people believe the money should be spent elsewhere in the health service

unethical - some healthy embryos are destroyed; there’s a possibility that in the future we may be able to produce offspring with desire-able features through screening