SB3

Question 1

1) Define sexual reproduction
2) What organisms use it?
3) Describe the offspring produced

Answer 1

1) Fertilisation of gametes requiring two parents
2) Most animals and plants, including humans
3) The offspring have combined characteristics from their parents + offspring are different from one another

Question 2

Sexual Reproduction
1) Advantages
2) Disadvantages

Answer 2

1) More likely to adapt to new environments and diseases, more variation
2) Takes longer, a parent’s negative characteristics / diseases can pass on

Question 3

1) Define asexual reproduction
2) What organisms use it?
3) How can plants grow their offspring?
4) Describe the offspring produced

Answer 3

1) Requires one parent and occurs due to mitosis
2) Common in invertebrates
3) Through runners/ roots
4) Offspring are identical and clones of their parent

Question 4

Asexual Reproduction
1) Advantages
2) Disadvantages

Answer 4

1) Quicker, beneficial when lots of food is available, aphids can make the most of food available, positive characteristics can spread
2) Same reaction to diseases, less variation

Question 5

1) Define a genome
2a) When is meiosis used in humans
2b) Why?

Answer 5

1) The DNA of an organism
2a) To produce gametes
2b) The offspring need only 2 copies of each chromosome whereas if two gametes fertilise, they need only 1 copy of each chromosome each to combine producing a zygote with 2 copies of each chromosome

Question 6

Describe the steps of meiosis

Answer 6

DNA replication causes chromosomes to replicate. The chromosomes stick together. The cells then divide into two two times producing 4 daughter cells with one copy of each chromosome from each pair. They’re haploid.

Question 7

DNA
1) Structure + the sections it’s made of
2) The bases in pairs + their hydrogen bonds
3) What is a nucleotide

Answer 7

1) A polymer double helix + made from nucleotides
2) Adenine + Thymine (2 bonds) Cytosine + Guanine (3 bonds)
3) A base, sugar and phosphate group

Question 8

Why do people have different genes?

Answer 8

Due to different orders of bases in our DNA

Question 9

Transcription

Answer 9

RNA polymerase attaches to DNA. Enzymes separate the two strand of DNA. Complementary nucleotides are adds and they link to form mRNA

Question 10

Translation

Answer 10

mRNA leaves the nucleus. It attaches to ribosomes in the cytoplasm. At each codon, tRNA and complementary bases line up. Amino acids from tRNA join to form polypeptides

Question 11

Alleles
1) Definition
2) Homozygous / heterozygous
3) Dominant + recessive

Answer 11

1) different forms of the same gene
2) alleles in a gene that are the same/ different
3) Dominant alleles have an affect, recessive alleles don’t

Question 12

1) Genotype
2) Phenotype

Answer 12

1) An organisms alleles
2) An organisms characteristics/looks

Question 13

Sex chromosomes
1) Male / Female
2) Punnett squares show…
3) Family Pedigree Charts show…

Answer 13

1) XY / XX
2) Possible outcomes for an offspring’s genotype
3) A family’s inherited genotypes + phenotypes

Question 14

Blood Types
1) 4 different groups
2) Allele representation for blood groups
3) Recessive + dominant blood types

Answer 14

1) A, B, AB or O
2) IA, IB, IAB or IO
3) Blood types A and B are dominant, blood type O is recessive

Question 15

What blood group would a person be with alleles:
1) IA + IA
2) IB + IB
3) IA + IB
4) IA + IO or IB + IO

Answer 15

1) A
2) B
3) AB
4) A or B

Question 16

Sex linked disorders
1) What would happen if a male had one allele for a sex linked disorder

Answer 16

1) If a male had an allele for a sex linked disorder, he would definitely have that disorder as males only have one X sex chromosome and can only carry one sex-linked disorder allele.
(eg. if r = affected, R = unaffected)
if a male was XrY they’re affected, if a male was XRY they are unaffected.

Question 17

What would happen if a male had a allele for a sex-linked disorder.

Answer 17

They’d definitely have it because males only have one X sex chromosome and only the X sex chromosome can carry alleles for sex-linked disorders, the Y sex chromosome can’t carry these alleles. eg. if r = affected, R = unaffected and a male was XrY they’d be affected. if a male was XRY they’d be unaffected.

Question 18

1)What is a mutation
2) What might it happen through
3) Why can it happen

Answer 18

1) A change in a gene that creates a new allele
2) Usually occurs through cell division. 3) It can happen naturally or through DNA damage such as radiation or due to substances

Question 19

1) What’s the human genome project
2) Who helped create the human genome project
3) Why is mapping genomes helpful

Answer 19

1) A map of billions of different complementary base pairs
2) Lots of scientists around the world
3) It can help find out if people are likely to develop certain diseases and can help identify the best treatment/ medicine

Question 20

1) Define Genetic variation
2) Give some examples

Answer 20

1) Variation caused by inherited alleles through sexual reproduction
2) Blood group, skin colour, eye colour, ear type and natural hair colour

Question 21

1) Define Environmental variation
2) Give some examples
3) What are acquired characteristics

Answer 21

1) Variation affected by surroundings
2) Scars, piercings, tattoos, language
3) Characteristics changed through the life of an individual (eg. lost leg)

Question 22

Give some examples of genetic and environmental variation

Answer 22

Height/ weight