Section 7 - Inherited change Flashcards
What is a gene?
An inherited instruction which codes for a polypeptide
What is an allele?
Different version of the same gene due to a mutation
What is a genotype?
The genetic constitution of an organism
What is a phenotype?
Observable traits of an organism
What does homozygous mean?
When the allele on each chromosome is the same
What does heterozygous mean?
When the allele on each chromosome is different
What does codominant mean?
When 2 alleles both contribute to the phenotype
What is a monohybrid cross?
A cross in which the alleles of only one gene are involved
What are the steps to formulating a monohybrid cross?
- Determine gametes from each parents
- Create a punnet square
- Determine phenotypic ratio
What is codominance?
When alleles share dominance of a characteristic
-When both codominant alleles are present, phenotype shows mixture of characteristics
What is the expected ratio/ percentage of homozygous codominant genetic cross?
100% blended allele
white + red = pink
What are the 4 different blood groups?
AB, A, B, O
What is the expected ratio of a heterozygous codominant genetic cross?
1:1:1:1
25% of each
What is the genotype of the blood group A?
AA or AO
What is the genotype of the blood group B?
BB or BO
What is the genotype of the blood group AB?
AB
What is the genotype of the blood group O?
OO
What is dihybrid inheritance?
Inheritance of 2 genes (with 2 different alleles each) on different chromosomes.
As alleles are on different chromosomes they can pass into the gametes in any combination
What is a dihybrid cross?
A cross in which the alleles of 2 different genes are involved.
What is the expected phenotypic ratio for a heterozygous dihybrid cross?
9:3:3:1
What is a test cross?
Cross in which one of the individuals is homozygous recessive
What is the expected ratio of a recessive and heterozygous dihybrid cross?
1:1:1:1
What are linked genes?
Describes genes whose loci are on the same chromosome.
What is autosomal linkage?
Applies to genes which are non-sex chromosomes
What would the gametes from AaBb be if the genes were linked?
AB
ab
What are the sex chromosomes for most male and female?
Males- XY
Females- XX
What sex chromosomes is bigger and carries more genes?
X chromosomes
What is one limitation of using a line transect to collect data?
Transect line may not go through representative area
What are two features of a climax community?
Abiotic factors are constant
Populations are stable around carrying capacity
Same species is present over long time
Why are recessive characteristics more common in males?
No homologous allele present
Characteristics caused by recessive allele have greater chance of appearing
Will appear even through there is only 1 copy
What is the chi-squared test?
Used to assess if observed results are significantly different to those expected
Data must be categorial and consist of raw values
Degrees of freedom: classes -1
What is a null hypothesis?
There’s no difference between observed and expected results
In the chi-squared test, if the calculated value is LESS than the critical value then…
Accept null hypothesis
More than 95% probability any difference is due to chance
No significant difference between observed and expected results
In the chi-squared test, if the calculated value is MORE than the critical value…
Reject null hypothesis
Less than 5% probability that results are due to chance
Significant difference between observed and expected results
What is epistasis?
When the alleles of one gene mask the expression of the alleles of another gene
What is dominant epistasis?
A dominant allele at one gene locus masks the expression of alleles at a second gene locus
What is the expected ratio of a heterozygous cross involved in dominant epitasis?
12:3:1
What is recessive epistasis?
Two recessive alleles at one gene locus will mask the expression of alleles at a second gene locus
What is the expected ratio of a heterozygous cross involved in recessive epitasis?
9:3:4
What is linkage?
2 or more genes on same chromosome, inherited together
What is epistatsis?
The interaction between 2 alleles
Suggest one reason why observed ratios are often not the same as expected ratios?
Fertilisation is random
Fusion of gametes is random
Sample is small
