Chapter 17 - Inherited Change Flashcards
What is the genotype of an organism?
All the alleles possessed by an organism
What is the phenotype of an organism?
Observable characteristics
What two factors contribute to the phenotype?
Genetics and environment
What is a gene?
Length of DNA, codes for polypeptide
What is the locus?
Position of gene on DNA strand
What is an allele?
Different forms of genes
What are codominant alleles?
Both contribute to phenotype
What are multiple alleles?
More than two alleles
What is pure breeding?
Organisms have two of the same alleles for a gene
What is a ratio?
A proportion
Why are the predicted results rarely the same as the observed results?
Only a prediction
Chance
Small sample
What is dihybrid inheritance?
Looking at how two genes on different chromosomes are inherited
How do you work out a dihybrid cross?
Do the same as a normal cross but include both genes
Which genotypes result in blood group A?
IA, IA or IA, IO
Which genotypes result in blood group B?
IB, IB or IB, IO
Which genotypes result in blood group AB?
IA, IB
Which genotypes result in blood group O?
IO, IO
What is autosomal linkage?
Two or more genes are carried on the same autosome
What impact does autosomal linkage have on a genetic cross?
Rather than having AB, ab, Ab, aB, you only have AB and ab because the two are linked
What is epistasis?
One allele affects or masks the expression of another
Explain epistasis in mice
Gene A (black bands) is affected by the expression of B (production of melanin)
bb means no melanin and an albino mouse
B means melanin is produced
If A is also present, there is a black-banded mouse
If a is also present, there is a black mouse
What does the Chi-squared test do?
Test the null hypothesis
What is the null hypothesis?
There will be no statistically significant difference between our expected and observed values
What requirements does the Chi-squared test have?
Large sample size
Discrete categories
Raw counts, not percentages
Formula for Chi-squared
https://www.statisticshowto.datasciencecentral.com/wp-content/uploads/2013/09/chi-square-formula.jpg
What are the degrees of freedom?
One less than the number of categories
If the probability that the data is due to chance is bigger than 5%, what do we do?
Accept the null hypothesis - the deviation is insignificant
If the probability that the data is due to chance is less than 5%, what do we do?
Reject the null hypothesis - the deviation is significant
Why will characteristics that are controlled by recessive alleles on the non-homologous section of the X chromosome appear more frequently in males?
There is no homologous section on the Y chromosome that may contain the dominant allele
Example of X linked disease?
Haemophilia
Where must males get their Y chromosome from?
Their father
What is the law of independent assortment?
Each member of a pair of alleles may combine randomly with either of another pair
How can results of genetic crosses be made to be closer to predicted ones?
By using a very large, representative sample
Why are actual results of genetic crosses rarely the same as predicted?
Due to statistical error
What is the law of segregation?
In diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete.
Which sex chromosomes do females have?
XX
Which sex chromosomes do males have?
XY
How many different types of gamete do males produce?
2, one X and one Y
What are sex-linked genes?
Any gene carried on wither the X or Y chromosome
Why can some genes be more prevalent in males than females?
The X chromosome is much longer than the Y, so more most of the X chromosome, there is no homologous equivalent and those recessive characteristics on the X chromosome will be more frequent in males
