6.1.2 pattern of inheritance / evolution

what does genotype mean?

the Alleles of a organism

what does phenotype mean?

the physical characteristics of a organism

what is a allele?

different version of the same gene

what does the dominant gene mean

gene that’s always expressed ( makes the protein )

what does the recessive gene mean?

only expressed when both genotypes are recessive

how are recessive genotype shown?

aa ( lower case letters)

how are Dominant genotypes shown?

AA ( upper case letters)

what does homozygous mean

2 identical alleles

what does heterozygous mean

2 different alleles

what are the types of genotypes

monogenic

polygenic

what factors affect phenotype

environmental and genotype

what does monogenic mean

1 gene controls characteristics

what does polygenic mean

multiple genes control characteristics

what are the two phenotypic variation in plants

chlorosis

Etiolation

what are the two phenotypic variation in plants caused by

the environment

Chlorosis meaning and what causes it ?

Plants don’t produce enough chlorophyll and turn yellow

Lack of Mg in the soil

Etiolation meaning and what causes it ?

plants grow abnormally long and spindly

due to a lack of sunlight

Codominant definition

both alleles are expressed in a phenotype

Carrier definition

A Organism carrying an allele which is not expressed in the phenotype

Monogenic Punnet square

How to complete a punnet square

1) show parents genotype

2) show the gametes

3) times the letter ( FOIL)

4) produce punnet square

what is the usual ratio for Dihybrid crosses between two heterozygous parents

9 : 3 : 3 : 1

how to work out offspring genotype in punnet square

allele x allele ( RY X rY) = RrYY

how to work out gametes in punnet square

FOIL ( first outer inner last)

Dihybrid punnet square image

Explain why observed results don’t match predicted results 

sex linkage occurred 

what do sex chromosomes in a question mean

there’s sex linkage

what is the superscript in sex chromosomes

the alleles

difference between discontinuous and continuous variations

discontinuous → categorical / qualitive data

continuous → quantitative data

what is discontinuous variation controlled by

1 or few genes

how many genes cause continuous variation

many genes 

graph type for discontinuous variation  

Bar chart

graph type for continuous variation  

Histogram

histogram image

how to know if a graph/ bar chart is affected by environmental factors 

Bell curve shape shows normal distribution 

bell curve shape ( Image)

what are the sex chromosomes for male and female in mammals

male → XY

female → XX

description of sex chromosomes in mammals

males are heterogametic ( XY) 

females are homogametic ( XX)

what does sex linked characteristic mean

alleles that code for them are located on Sex chromosomes

why are males more likely to have X- linked disorders

males have XY chromosomes

1 X chromosome → expressed when recessive

what is autosomal linkage 

genes close together are linked so they  stay together during independent assortment of chromosomes .

what is epistasis

allele of a gene inhibits the expression of other genes alleles.

when would you use X² test 

test the difference between prediction and phenotype 

X² square test equation

X² square test how to work out expected value

(total number of offspring / ratio total) x predicted ratio

X² square test example image

how to work out degrees of freedom in X² square

(number of phenotypes) - 1

when do you accept null hypothesis in X²

Accept null hypothesis when X² is less then critical value shows there no significance difference between expected and observed results

more then 5% probability results are due to chance

when do you reject null hypothesis in X² square 

reject null hypothesis when X² value is equal / greater then critical value shows there a significant difference between expected and observed results.

less then 5% probability results are due to chance

gene pool definition 

compete range of alleles in a population

allele frequency definition

how often a allele occurs in a population

what does a small gene pool result in

low variation , low allele frequency

what is a selective pressure 

something in the environment that gives a specific allele a advantage

Are selective pressures natural or artificially occuring

Both

artificial in selective breeding

what are the types of natural selection

Directional

stabilising

Disruptive

natural selection process

Random mutation in DNA creates a new allele 

selective pressure creates struggle for survival

selective pressure selects specific alleles that are advantageous 

individuals with allele are more likely to survive and reproduce - pass allele to offspring 

over many generations → allele frequency in population increases

what does a larger bell curve mean on a graph 

larger gene pool 

Graph ( image)

what is Directional selection

individuals are favoured in one direction

what is disruptive selection

extremes are favoured 

what is stabilising selection

average individual favoured

Directional selection image

temperature decreases → longer fur population increases becomes average

moves right 

effect of stabilising selection on population  ( image)

mean remains the same but fewer extremes

what causes speciation

disruptive selection

what is disruptive selection

natural selection that maintains high frequencies of two different sets of alleles.

what are the ways evolution can occur ?

Natural selection

Genetic drift

genetic bottleneck

what is evolution by Genetic drift ?

particular alleles which are passed down a in population due to chance.

no selection

Genetic drift effect ?

increases allele frequency 

Differences Genetic drift and natural selection

genetic drift → no allele selection / due to chance

Genetic bottleneck effect of the gene pool

reduces gene pool

what is Genetic bottleneck?

a event occurs that removes majority of population → small gene pool in survival paper

Genetic bottleneck ( Image)

what is the founder effect

post bottleneck founding a new population

hardy Weinberg equations

when is Hardy Weinberg equation used ?

Predict ratio of Dominant / Recessive allele in population

assumption made when using Hardy Weinberg equation used

no mutations → no new allele

no selection → no allele favoured

random mating

how to improve Hardy Weinberg equation

use a larger sample size → accurate

allele equation Hardy Weinberg

when can Hardy Weinberg equation used

Heterozygous cross

phenotype and genotype Hardy Weinberg