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Question 1

Describe the stages of embryonic development

Answer 1

Starts as 8 identical cells - zygote

5 days after conception - blastocyst forms

Then outer blastocyst cell layer forms placenta

Inner cell mass of 50 cells form the embryo tissue - pluripotent stem cells

Question 2

What is a human zygote

Answer 2

8 identical cells, all totipotent

Question 3

What is a blastocyst

Answer 3

Hollow ball of cells that forms after 5 days of conception

Question 4

What are totipotent cells

Answer 4

Total potential so can develop into a human and all cell types

Question 5

What are pluripotent cells

Answer 5

Potentially give rise to most cell types not all

Question 6

What are multi-potent cells

Answer 6

Adult stem cells

Give rise to some cell types

Question 7

What is the hardy Weinburg equation

Answer 7

P squared + 2pq + q squared = 1

Freq of homozygous dominant 
PLUS
freq of heterozygous individuals
PLUS
freq of homo recessive individuals

Question 8

What is hardy weinburg used for

Answer 8

Used to see change in allele freq over time

Question 9

What are P and Q in hardy W

Answer 9

Dominant = P

Recessive = Q

Question 10

10 stages of fertilisation

Answer 10

1- sperm reach ovum
2- chemicals released, triggers acrosome reaction
3- acrosome swells, fuses with sperm cell membrane
4- digestive enzymes released from acrosome
5- enzymes digest through follicle cells
6- enzymes go through zona pelucida
7- sperm fuses with ovum membrane
8- sperm nucleus enters ovum
9- enzymes released from lysosomes in ovum, thicken jelly like later
10- nuclei of the ovum and spent fuse

Question 11

6 parts of sperm

Answer 11

Acrosome
Head 
Middle
Flagellum
Motiochondrion
Nucleus

Question 12

7 parts of ovum

Answer 12

Cytoplasm
Haploid nucleus
Lysosomes
Follicle cells
Zona pellucid
Lipid droplets
Cell surface membrane

Question 13

What is sex linkage

Answer 13

Characteristics become sex liked when the locus of the allele that code for it is on a sex chromosome

Question 14

How are T cells activated

6 stages

Answer 14

Bacteria with antigens in surface enter the body
Macrophage engulfs
M presents the antigens and becomes antigen presenting cell
T helper cells with complementary receptors (CD4) binds to antigens
T helper activated and divides
Created clones of T memory and helper
Quicker response

Question 15

What are T cells

Answer 15

Type of lymphocyte
Specific immune response
T helper - stimulates. Cells which make antibodies and enclave phagocytes

T killer - destroys foreign antigens

Question 16

2 stages of photo synthesis
What they use and make
Where

Answer 16

Light dependent 1st stage
Used light energy and H20
Makes reduced NADP and ATP and waste product of O
Thylakoid

Independent 
Uses reduced NADP and ATP
makes C6H12O6 
Reduced CO2 into carbohydrates 
Stroma

Question 17

Light dependent stage

6 stages

Answer 17

1. Light energy raises 2 electrons in each chlorophyll molecule- excited state
2. Elections leave, travel on electron carries molecules forming electron transport chain
3. Electrons from PS2 pass from carries = losing energy. Energy is used phosphorylation for ATP
4. Electrons from PS2 replace PS1
5. Enzyme catalysed photolysis( O2,hydrogen ions + electrons)
6. Electrons from PS1 combine with co - enzyme NADP + hydrogen ions from water = reduced NADP

Question 18

Stages of speciation

Answer 18

Reproductive isolation usually from geographical but can be temporal, behavioural, habitat
Prevents interbreeding
Less similar different selection pressures
Random Mutations
Different alleles
Can’t successfully interbreed
No fertile offspring

Question 19

Define gene pool

Answer 19

All the alleles of all the bees present in a population

Question 20

Allele freq equation

Answer 20

P+q=1

P is dominant
Q is recessive

Only used with 2 alleles for one gene

Question 21

What is the structure of collagen

Answer 21

It’s a fibrous protein so it’s stick teal and insoluble

3 polypeptide chains held together by hydrogen bonds
With cross links for extra strength