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Biology OCR GCSE > B5.1 Inheritance > Flashcards

B5.1 Inheritance Flashcards

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
Genome
All the genes present in an organism, entire genetic material of an organism 3 levels of organisation of a genome: DNA Chromosomes Genes
26
What happens during fertilisation
The nuclei of two haploid (n) gametes fuse to produce a single diploid (2n) cell known as a zygote
27
How are gametes made
Meiosis 4 haploid genetically identical cells made from 1 parent cell
28
Stages of meiosis
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
Compare mitosis and meiosis
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
Difference between dipoild and haploid cells
Haploid cells have 1/2 the amount of genetic information as diploid cells Haploid cells are gametes Diploid cells are somatic cells
31
Type of cell meiosis produces
Gametes (Haploid)
32
How dominant alleles are represented in a Punnett square
Uppercase letters
33
How recessive alleles are represented in a punnet square
Lowercase version of the same letter as the dominant allele
34
Mutation
Random change in sequence of DNA bases that can be inherited Permanent change in nucleotide sequence of DNA
35
Mutagen
Substances or conditions that increase the chance of a mutation occurring Ionising radiation Benzene Ethanol Smoking
36
How mutation in coding DNA sequnece could be detrimental
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
How a mutation in a non-coding DNA sequnece could be detrimental
May stop transcription and alter expression of genes
38
Negative examples of gene mutations
Huntington’s disease Sickle cell anaemia Cystic fibrosis Cancer Alpha & Beta thalassemia Tay-sachs disease Phenylketonuria Hemochromatosis Marfan Syndrome
39
Neutral examples of gene mutations
Tongue rolling Polydactyly Joined ear lobes Most mutations are neutral
40
Examples of beneficial gene mutations
Antibiotic resistance in bacteria Colouring that aids camoflauge De-pigmentation in cold/dark climates Production of lactose post-infancy
41
Important findings of Gregor Mendel
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
Discovery leading people to accept Mendel’s ideas
Discovery of genes
43
Which is faster: sexual or asexual production
Asexual
44
If an organism can reproduce sexually or asexually…
Often reproduces asexually when conditions are optimum
45
What holds 2 strands of DNA together
Attraction between bases
46
How many bases used to code for an amino acid
3 organic bases (bases read in triplet codons)
47
Advantages of embryonic screening
Prevent suffering Financial savings
48
Why effects of most mutations are not observed
Most mutations do not affect phenotype
49
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
Controls expression of gene 2
50
'junk' DNA
Non-coding DNA that can control transcription Can turn genes on/off so they can/can't make specific proteins
51
How a mutation in non-coding DNA can change activity of a cell
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
Why a sample of 100 people is unlikely to show 55 people with brown eyes, and eight people with blue eyes
Sample size too small, so random variation would not affect it
53
F1 Generation
Generation immediately after the first parents

Biology OCR GCSE (16 decks)

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