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Biology OCR GCSE > B5.1 Inheritance > Flashcards

B5.1 Inheritance Flashcards

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1
Q

Variation

A

Differences within species
Caused by mutations in genetic code

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2
Q

Examples of variation

A

Height
Build
Eye colour
Hair colour
Blood group
Language

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3
Q

2 causes of variation within species

A

Genetics
Environment

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4
Q

How variation of a characteristic displayed can be further categorised

A

Continuous vs discontinuous variation

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5
Q

Discontinuous variation

A

Variation that produces distinct categories:

Eye colour
Blood group
Gender

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6
Q

Continuous variation

A

Variation that cannot be placed in distinct categories and instead produces a spectrum:

Height
Weight
Skin colour

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7
Q

What type of variation will human body mass display

A

Continuous

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8
Q

Asexual reproduction

A

Offspring is clone of parent
No gamete fusion
Only 1 parent required

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9
Q

Examples of organisms that can replicate asexually

A

Potato plants
Stawberries
Spider plants
Bacteria
Mushrooms
Daffodils

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10
Q

How does asexual reproduction take place

A

Mitosis
Only 1 parent needed
Identical clone produced

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11
Q

Sexual reproduction

A

Requiring two parents
Genetic information taken from both parents
Organisms produce haploid gametes that fuse during fertilisation
Offspring not identical / clone of parents
Results in variation

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12
Q

Advantage and disadvantage of sexual reproduction

A

+
Variation in offspring leads to adaptation in a species
This results in some organisms within a species containing adaptations that allow them to cope with an environmental pressue.
These organisms can reproduce, enabling the species/population to survive.

-
Reproduction requires two parents.
Reproduction is slowers, so few offspring are produced in a given time

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13
Q

Advantage and disadvantage of asexual reproduction

A

+
If the parent was well adapted to an area then the offspring will share an identical set of characteristics
Only one parent is needed - animals do not need to find a partner, plants do not require pollination
Faster, so large numbers of offspring are produced quickly

-
Adverse changes to the biotic or abiotic factors may destroy the species, as all organisms affected due to there being no variation

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14
Q

Gamete

A

Sex cell
Haploid cell used in sexual reproduction
Sperm & egg
Pollen & ovule

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15
Q

Chromosome

A

Tightly packaged DNA,
wrapped around histone proteins

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16
Q

Gene

A

Section of DNA that can (but not always) code for a protein

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17
Q

Allele

A

Different versions of same gene
Eg. blue eyes vs. green eyes

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18
Q

Dominant allele

A

Version of a gene where only one copy is required for it to be expressed in the organisms phenotype

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19
Q

Recessive allele

A

Version of a gene where two copies are required for it to be expressed in the organisms phenotype

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20
Q

Pure breeding

A

Organism is homozygous for a characteristic

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21
Q

What is meant when an organism is homozygous

A

When an organism has 2 copies of the same allele (either both dominant or both recessive)

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22
Q

What is meant when an organism is heterozygous

A

When an organism has two different version of the same gene (one dominant and one recessive)

23
Q

Genotype

A

Genes present for a trait
Includes all the genes that are being expressed and not expresses

24
Q

Phenotype

A

Visible characteristics displayed as a result of an organisms genotype

25
Q

Genome

A

All the genes present in an organism, entire genetic material of an organism

3 levels of organisation of a genome:
DNA
Chromosomes
Genes

26
Q

What happens during fertilisation

A

The nuclei of two haploid (n) gametes fuse to produce a single diploid (2n) cell known as a zygote

27
Q

How are gametes made

A

Meiosis
4 haploid genetically identical cells made from 1 parent cell

28
Q

Stages of meiosis

A

Stage 1:
Chromosomes are copied
Chromosomes line up upon the midline of the cell in pairs (one from the father, one from the mother)
Spindle fibres form
Spindle fibles contract towards opposite poles
1 member of each pair is pulled to opposite ends of the cell - sections of DNA are often swapped at this stage (crossing over & recombination)
Cell divides in two form two separate cells

Stage 2:
Chromosomes line up upon the midline of each new cell
Spindle fibres form
Spindle fibles contract towards the oppostive poles
The chromosomes are pulled in half - a single copy of each chromosome goes to the opposite end of the cell
Each cell divides in two - results in four haploid (n), genetically different cells

29
Q

Compare mitosis and meiosis

A

Mitosis:
Cell divides once
Two cells produced
Same number of chromosomes as parent cell
Used for growth & repair
Happens in all parts of the body
Daugther cells genetically identical to parent cell

Meiosis:
Cell divides twice
4 cells produced
Half the number of chromosomes as parent cell
Used to produce gametes
Happens in reproductive organs only (testes/ovaries)
Daugther cells genetically varied cells to parent cell

30
Q

Difference between dipoild and haploid cells

A

Haploid cells have 1/2 the amount of genetic information as diploid cells
Haploid cells are gametes
Diploid cells are somatic cells

31
Q

Type of cell meiosis produces

A

Gametes
(Haploid)

32
Q

How dominant alleles are represented in a Punnett square

A

Uppercase letters

33
Q

How recessive alleles are represented in a punnet square

A

Lowercase version of the same letter as the dominant allele

34
Q

Mutation

A

Random change in sequence of DNA bases that can be inherited
Permanent change in nucleotide sequence of DNA

35
Q

Mutagen

A

Substances or conditions that increase the chance of a mutation occurring
Ionising radiation
Benzene
Ethanol
Smoking

36
Q

How mutation in coding DNA sequnece could be detrimental

A

DNA bases within the coding gene may be changed, added or deleted
Changes sequence of bases, so order of bases produced during transcription is altered
Then alters amino acids coded for in translation affecting the protein produced
-> be the wrong protein, or fold incorectly and form a different shape
-> may then affect the protein, particularly in specific molecules like enzymes and antibodies

37
Q

How a mutation in a non-coding DNA sequnece could be detrimental

A

May stop transcription and alter expression of genes

38
Q

Negative examples of gene mutations

A

Huntington’s disease
Sickle cell anaemia
Cystic fibrosis
Cancer
Alpha & Beta thalassemia
Tay-sachs disease
Phenylketonuria
Hemochromatosis
Marfan Syndrome

39
Q

Neutral examples of gene mutations

A

Tongue rolling
Polydactyly
Joined ear lobes

Most mutations are neutral

40
Q

Examples of beneficial gene mutations

A

Antibiotic resistance in bacteria
Colouring that aids camoflauge
De-pigmentation in cold/dark climates
Production of lactose post-infancy

41
Q

Important findings of Gregor Mendel

A

Characteristics are determined by hereditary units (now refered to as genes)
Offspring recieve units from both parents, one unit from each, so share traits with both parents
Hereditary units are dominant or recessive, so traits not always visible

42
Q

Discovery leading people to accept Mendel’s ideas

A

Discovery of genes

43
Q

Which is faster: sexual or asexual production

A

Asexual

44
Q

If an organism can reproduce sexually or asexually…

A

Often reproduces asexually when conditions are optimum

45
Q

What holds 2 strands of DNA together

A

Attraction between bases

46
Q

How many bases used to code for an amino acid

A

3 organic bases
(bases read in triplet codons)

47
Q

Advantages of embryonic screening

A

Prevent suffering
Financial savings

48
Q

Why effects of most mutations are not observed

A

Most mutations do not affect phenotype

49
Q

Gene 1 and gene 2 are both needed for the production of protein A:
What is the function of gene 1 in this process?

Gene 1 gene 2
|
V
Transcription
|
V
Translation
|
V
Protein A

A

Controls expression of gene 2

50
Q

‘junk’ DNA

A

Non-coding DNA that can control transcription

Can turn genes on/off so they can/can’t make specific proteins

51
Q

How a mutation in non-coding DNA can change activity of a cell

A

Can change amino acid sequence in a protein - transcription of mRNA may be stopped

Can turn genes on/off so they can/can’t make specific proteins

52
Q

Why a sample of 100 people is unlikely to show 55 people with brown eyes, and eight people with blue eyes

A

Sample size too small,
so random variation would not affect it

53
Q

F1 Generation

A

Generation immediately after the first parents

Biology OCR GCSE (16 decks)

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