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Biology A Level > Biology A2 > Flashcards

Biology A2 Flashcards

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1
Q

What is a sex linked gene/allele?

A

A gene (that will have multiple alleles of that gene) that is located on a sex chromosome (e.g. either the X or Y chromosome, though it is always always the X chromosome).

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2
Q

What is an example of a sex linked genes causing conditions affecting specific genders?

A

The genes that allow us to see red and green are found on the X chromosomes. Mutations in these gees can lead to colour blindness, so only 0.7% of females are colour blind, while 8% of males are colour blind.

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3
Q

What is the definition of a gene carrier?

A

An individual that has one copy of a recessive allele that causes a genetic disorder.

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4
Q

Define two autosomally linked gene

A

When two genes coding for different characteristics on a chromosome are located so close to each each other that the two alleles are always inherited together. (i.e. if the gene for hair length (alleles H- long and h-short) and hair colour (W-white and B-brown) were autosomally linked, the gene for white short hair would always be inherited together.

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5
Q

What is a coenzyme?

A

An enzyme that aids the function of other enzymes by transferring the chemical groups between the molecules being reacted.

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6
Q

What is the coenzyme associated with photosynthesis? ?

A

Nicotinamide Adenine Dinucleotide Phosphate (NADP)

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7
Q

What are the three key events in the light-dependent stage of photosynthesis?

A

Photoionisation
Photolysis
and Chemiosmotic Theory

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8
Q

How is light energy and chlorophyll used in photoionisation?

A

When chlorohyll molecules absorb light energy it boosts the energy within the electrons in the chlorophyll. This causes the electrons to leave the chlorophyll molecule, causing the chlorophyll molecule to become ionised. These electrons are then passed along “electron carrier” molecules by a series of oxidation and reduction reactions. The electrons lose a bit of energy with each reaction, and this “scrap” energy is then use to phosphorylate ADP to ATP.

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9
Q

How is light energy used in photolysis?

A

It is needed to split water into H+ and OH- ions. After photoionisation occurs, chlorophyll molecules are short of electrons and require more so they can continue to absorb light energy. These are provided when water is split into H+ and OH- ions in photolysis.

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10
Q

How are the products in photolysis used to support the Calvin Cycle?

A

Photolysis produces both electrons and protons. The protons exit the thylakoids to aid the calvin cycle in the stroma. Here, they bond with NADP to create reduced NADP. This is then used in the reduction stage of the calvin cycle, when the NADP releases H+ ions to turn Glycerate 3 Phosphate to Triose Phosphate.

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11
Q

What is the equation or photolysis?

A

2H2O →→→→ 4H+ (protons) and 4e- (electrons) and Oxygen (O2)

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12
Q

What are the three products of the light dependent reaction of photosynthesis used in the calvin cycle?

A

H+ ions, NADP and ADP/ATP.

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13
Q

What is stage one of the calvin cycle?

A

Carbon Fixation

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14
Q

What is the main (intended) input product of the calvin cycle and output product of the calvin cycle?

A

Input product- Carbon Dioxide

Output Product- Glucose

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15
Q

What is the name of the starting compund in the Calvin Cycle?

A

Ribulose Biphosphate

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16
Q

What happens during the Carbon fixation stage of the calvin cycle

Clues
- CO2, RuBP, 2x GP, Rubisco

A

Carbon Dioxide enters the leaf via th stomata and then enters the stroma of the chloroplasts. This then binds with the starting compound of the calvin cycle, Ribulose Biphosphate. This is then broken down into 2 Glycerate 3 phosphate molecules (a three carbon compound). This entire reaction is catalysed by a substance called Ribulose Biphosphate Carbulose

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17
Q

What products from the light dependent reaction are used in the reduction stage of the calvin cycle?

A

ATP and Reduced NADP

18
Q

What happens in the reduction stage of the Calvin Cycle?

GP →→→→ requires energy from ATP and H+ ions from NADP →→→→ TP

A

The 3 carbon molecule made in the former section of the calvin cycle (glycerate 3 phosphate) must be converted into another 3 carbon compound. In order to do this, it must require energy. ATP from the light dependent reaction is therefore hydrolysed to release this energy. H+ ions are also required to change the Glycerate 3 phosphate into triose phosphate (TP). These ions are obtained from the (reduced) NADP+, so the H+ ions are released, and the NADP+ can now be recycled as normal NADP. The Triose Phosphate is then used to make glucose (as well as other substances)

19
Q

What is the third stage of the calvin cycle?

A

RuBP Regeneration

20
Q

What happens in RuBP regeneration?

Clue—
TP x5 →→→→ energy from ATP hydrolysis →→→→ RuBP

A

AS RuBP is the starter compound of the calvin cycle, it must be regenerated each cycle. It does this using the Triose Phosphate made in the reduction phase. Only one of the 6 TP molecules made in three turns of the calvin cycle is used to create glucose (along with one other TP molecule from after another three cycles). The other five (after 3 cycles or ten after six cycles) are used to regenerate the RuBP. It does this through energy released from ATP hydrolysis.

21
Q

How many repeats of the calvin cycle does it take to create one glucose molecule?

A

6

22
Q

How many Triose Phosphate molecules does it take to make one glucose molecule?

A

2

23
Q

How many Triose Phosphate molecules are produced in 3 calvin cycles?

A

6

24
Q

How many ATP molecules are required for 6 turns of the calvin cycle?

A

18

25
Q

How many reduced NADP molecules are required for six turns of the calvin cycle?

A

12

26
Q

What is allele frequency?

A

How often a specific allele (often expressed in an allele dictated characteristic) occurs in a population

27
Q

What is gene pool?

A

All alleles of all the genes in the individuals that make up a population.

28
Q

What is speciation?

A

The evolution of a new species from an existing species

29
Q

What is the first step of speciation? What happens in this stage?

A

Gene pool isolation

The group gets cut off from the rest of the population/species group by a gene flow barrier (this can be physical or reproductive).

30
Q

What is allopatric speciation?

A

When the organisms in the gene pool isolation stage of speciation are geographically separated (e.g. the gene flow barrier is a physical barrier, such as a glacier or mountain or flood).

31
Q

What is sympatric speciation?

A

Though the organisms live in the same habitat at the same time, random mutations occur that cause an organism to be unable to reproduce with other individuals (gene flow barrier is reproductive).

32
Q

what is dihybrid inheritance?

A

When two genes controlling two different characteristics are inherited together.

33
Q

Define autosomal linkage

A

When two different genes are located on the same chromosome, so therefore are both inherited.

34
Q

What is discontinuous variation?

A

It is where individual specimen vary into a number of specific classes or categories. It can’t be measured across a complete range, so is often displayed in bar charts. It is usually qualitative data (i.e. eye colour or blood groups).

35
Q

What is continuous variation?

A

When a characteristic changes gradually over a range of values. It has no distinct categories, with no limit on the value it is measured by and it tends to be quantitative.. Examples could be weight or height, and it is usually displayed on a line graph/normal distribution curve. It is usually dictated by multiple genes and the environment.

36
Q

What is the role of the nucleolus?

A

It synthesizes ribosomes.

37
Q

How many hydrogen bonds are between the bases A and T?

A

Two hydrogen bonds

38
Q

How many hydrogen bonds are between the bases C and G?

A

Three hydrogen bonds

39
Q

What is the Hardy-Weinberg principle?

A

A principle stating that genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors. In order for this principle to apply there must be no selection, no mutation and random mating.It suggests that the proportion of dominant and recessive alleles will remain constant with each generation.

40
Q

What is one aspect of environmental variation?

A

Polygenes are susceptible to environmental variation.

41
Q

What type of variation is genetic variation?

A

Discontinuous variation

Biology A Level (10 decks)

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