Reproduction

Question 1

Haploid cells

Answer 1

Contain just 23 chromosomes

Question 2

Sexual reproduction

Answer 2

Male and female sex cell
Gametes fuse -> zygote
Meiosis
Inherit genes from both parents and characteristics
Won’t be identical

Question 3

Asexual reproduction

Answer 3

1 parent
Mitosis
No fusion of sex cells
No mixing of genetic information
No variation
Genetic material identical to parent

Question 4

Diploid cells

Answer 4

Contain 23 pairs of chromosomes

Question 5

Gametes

Answer 5

Sex cells
Haploid cells
Sperm and egg

Question 6

Fertilisation

Answer 6

Egg and sperm cell = 23 chromosomes
Fuse to form 46 chromosomes -> 23 pairs
Fertilisation complete = new cell divides by mitosis, number of cells increase, cells differentiate

Question 7

Meiosis process

Answer 7

1) Each chromosome is duplicated forming X-shaped chromosomes (46 from parent cells)
2) First division = chromosome pairs line up down the centre of the cell, pulled apart -> each new cell has one copy of each chromosome
3) Second division = chromosomes line up along centre of the cell with 23 pairs on each side and the arms of the chromosomes are pulled apart
4) Four haploid daughter cells produced = gametes

Question 8

Reproduction in fungi

Answer 8

Asexual
Moulds rot our food and reproduce asexually
Fungal spores produced by mitosis
Two hyphae join and nuclei fuse = hypha has 2 sets of chromosomes
Undergoes meiosis = haploid spores, each with 1 set of chromosomes
Spores may produce fungi better adapted to survive the adverse conditions

Question 9

Sexual Reproduction in plants

Answer 9

Gametes = pollen and egg produces using meiosis
Pollen reaches female parts of another flower = pollination
Once gametes fuse = seeds form
Introduces variation

Question 10

How are flowers adapted in reproduction?

Answer 10

Adapted to attract animal pollinators (insects, birds or bats)
To carry pollen to another flower

Question 11

Asexual reproduction in plants

Answer 11

New plants are formed even if flowers are destroyed by frost, eaten or fail to be pollinated
Disadvantage = new plants identical to parents = no variation

Question 12

Reproduction in malaria parasites

Answer 12

Asexual and sexual
Asexually in human liver and blood cells
Drop in temperature
Mosquito triggers sexual reproduction inside red blood cells
Sexual forms develop, burst out of the blood cells forms zygote with 2 sets of chromosomes
Zygotes undergo meiosis = produce asexual parasites

Question 13

What is DNA?

Answer 13

A polymer

Question 14

What are genes?

Answer 14

Small sections of your DNA
Determines inherited characteristics
Codes for sequence of amino acids to make a specific protein

Question 15

What do enzymes control in your DNA

Answer 15

Control your cell chemistry

Question 16

What is a genome?

Answer 16

Entire genetic material of the organism

Question 17

How does mitochondria affect our DNA?

Answer 17

Contain their own DNA

Inherit your mitochondrial DNA from your mother because it comes from the mitochondria in egg

Question 18

What does understanding genomes help people with?

Answer 18

Understanding inherited disorders
See peoples increased risk of developing many diseases
Predict risk for each individual = make lifestyle choices to help reduce the risk
Choosing the best treatment for a patient
Evolution and history

Question 19

What bases in the DNA always join together?

Answer 19

A and T

C and G

Question 20

What do the long strands of DNA consist of

Answer 20

Alternating sugar and phosphate sections

Attached to each sugar is a base

Question 21

What is a nucleotide?

Answer 21

Each unit of a sugar, phosphate and base

Question 22

How to make a protein

Answer 22

1) Template leaves nucleus and binds to surface of ribosome
2) Cytoplasm contains carrier molecules
3) Carrier molecules attach to the template of a specific amino acid
4) Amino acids join to form protein
5) Carrier molecules bring amino acids to add to protein chain
6) Protein detaches from carrier molecules
7) Carrier molecules detach from template and return to cytoplasm to bring more amino acids
8) Once protein shape is complete the molecules fold to form a unique shape to carry out its functions in the cell

Question 23

What happens if you change the order of the bases?

Answer 23

Alter the template resulting in a different sequence of amino acids
Changing the protein synthesised by the gene

Question 24

Describe the structure of a nucleotide?

Answer 24

A phosphate is attached to a sugar
Which consists of 4 bases
Which are A,C,T and G

Question 25

What do non-coding parts of the DNA do?

Answer 25

Switch genes on and off
Explain how we can synthesise so many different chemicals with so few genes
Affect how genes are expressed
Affects the phenotype (physical appearance)

Question 26

How is a mutation formed

Answer 26

When new genes form changes in existing genes

Mistakes made in copying the DNA for new cells as they reproduce

Question 27

What do some mutations code for?

Answer 27

Change in the amino acids alter protein folds to give a different shape
Active site of enzyme can no longer fit the substrate, loses its strength

Question 28

What is an allele

Answer 28

Each of 2 or more alternative forms of a gene that arise by mutation, found at the same place on a chromosome

Question 29

Homozygote

Answer 29

2 identical alleles

Question 30

Heterozygote

Answer 30

Different alleles

Question 31

Genotype

Answer 31

Describes alleles present or genetic makeup of an individual

Question 32

Phenotype

Answer 32

Physical appearance

Question 33

Where does a genotype work

Answer 33

At the level of the DNA molecules to control the proteins made

Question 34

What information does a punnet square give us

Answer 34

Alleles for a characteristic carried by parents
Possible gametes that can be formed
How gametes may combine to form characteristic in their offspring

Question 35

What is Polydactyly

Answer 35

Born with extra fingers or toes

Question 36

How does someone get Polydactyly

Answer 36

Inherited from 1 parent

50% chance of passing disorder on = half your gametes will contain the faulty dominant allele

Question 37

What does cystic fibrosis affect?

Answer 37

Organs of the body

Question 38

What is cystic fibrosis?

Answer 38

Cell membranes prevent the movement of certain substances from one side to the other

Question 39

What happens as a result of cystic fibrosis

Answer 39

Mucus made by cells becomes very thick and sticky
Organs are clogged up = stop working properly
Pancreas cannot secrete enzymes = tubes which enzymes are released is blocked
Most are infertile

Question 40

Treatments for cystic fibrosis

Answer 40

No cure
Physiotherapy = clear lungs
Antibiotics = replace enzymes in pancreas that cannot be produced

Question 41

What is cystic fibrosis caused by?

Answer 41

Recessive allele inherited by both parents
1/25 have allele
Most are unaware they have it

Question 42

Curing genetic disorders

Answer 42

No cures
Very serious and short lives
Genetic engineering = looking at replacing faulty alleles with health ones and gene replacement

Question 43

What is an amniocentesis test

Answer 43

Taking fluid from around foetus used for genetic screening

Question 44

What is chorionic villus

Answer 44

Sample of tissue for placenta

Using fetal cells to genetically screen foetus

Question 45

Carrying out screening

Answer 45

DNA isolated form embryo cells and tested for specific disorders

Question 46

Concerns about embryo screening

Answer 46

-Increase risk of miscarriage
+becoming more reliable and accurate
-can give false positive or negative test results
-have to make decision to keep or terminate pregnancy = science cannot help
-expensive
-risk to a demand character (people wants certain sex or intelligence)