6.2 Patterns Of Inheritance Flashcards
How can genetic diversity be measured
by looking at the number of polymorphic genes
Phenotype
visible characteristics of an organism e.g. blue eye vs green eye.
What is phenotype a combo of
environment + genetics = could include diet in animals.
What’s etiolation and what’s the effect of it
different environmental conditions (presence or absence of light) can influence if they have a strong or weak stem = in etiolation they always have a weak stem. also affects the colour in plants as well genetics.
Chlorosis
when the leaves produce insufficient chlorophyll due to mineral deficiencies e.g. iron
Genotype
genetic makeup of an organism (combination of alleles)
What can lead to genetic variation.
Meiosis, random fusion of gametes
What do mutagens do
Increase rate of gene mutation
What categories can mutagens be split into
physical (x rays, uv light, gamma rays), chemical (tar, free radicals, nitrous acid) and biological agents (viruses)
Types of chromosome mutation
Deletion
Inversion
Translocation
Duplication
Non disjunction
Deletion
- part of a chromosome is lost/deleted
Inversion
- Section of a chromosome breaks up, turns 180 degrees then joins together again
What’s the problem w inversion
even though u still have the same content the genes can be far away from the regulatory sequences
Translocation
- piece of chromosome breaks up and gets attached to another chromosome
- This effects the expression of genes
Duplication
- when a piece of chromosome becomes duplicated = double amount you need
- Causes over expression which can be dangerous
Non disjunction
- one pair of chromosomes failed to separate during meiosis and it can lead to gametes w extra chromosomes
Subtypes of non disjunction
Aneuploidy, polyploidy
Aneuploidy
chromosome number is not an exact multiple of the haploid number for that organism
Polyploidy
fusion of gametes results in an abnormal chromosome number = more than 2 sets of chromosomes
Effect of environment
can cause genetic variation but they don’t get passed on e.g. hair colour, piercings
Effects of a mutation on a protein
- could code for proteins that could be harmful, advantageous or neutral
Ways genetic variation occurs in meiosis:
- crossing over in prophase 1
- Independent assortment of chromosomes in metaphase 1
- Independent assortment of chromatids in metaphase 2
- Choice of gamete at the end is random - random fertilisation
Monogenic inheritance
- phenotypes or traits that are controlled by one gene e.g. cystic fibrosis is only caused by one gene
Study ab Monogenic inheritance
- Mendel did experiment on peas looking at ones w diff traits and saw what happened
Homologous chromosomes
every chromosome except x and y= same size, same shape, same gene at same loci
Genetic diagram for Monogenic inheritance
First one = pure breeding = two homozygous parents = produces first generation
F1 = first generation breeding = should be 2 heterozygous parents
ALWAYS WRITE A KEY. E.g. T = tall stem and t = short stem
Punnett square for Monogenic inheritance
expected ratio for cross f1s in a mono hybrid inheritance
3:1
Dihybrid inheritance
2 gene locis that get inherited together
expected ration for cross f1s in a dihybrid inheritance
9:3:3:1
Genetic diagram for Dihybrid inheritance
Multiple alleles
- When a gene has multipley alleles e.g. blue, green, red, brown eye
Codominance
2 alleles are dominant and come up in the phenotype together
Heretic diagram showing Codominance
A and B blood groups = dominant
O = recessive
Girls and guys sex chromosome?
- girls have XX and guys have XY
Which sex chromosome carries more genes + why
- Letter x is slightly longer than y so X chromosome carries more genes that aren’t present on the Y chromosome
Effect of X chromosome being slightly longer
- Any recessive trait linked to the X chromosome means guys are more at risk of getting it because they only need one of the recessive allele for it to be present
Why can females be symptomless carriers of recessive x linked disease
- In XX, a recessive x linked disease, females can be symptomless carriers. But male’s XY combination means that they can’t be carriers, they only have one X
Example of X linked disease + effect on males
- Haemophilia is a blood disorder where the blood can’t clot properly. The gene for blood clotting is carried on the X chromosome and males are more likely to get it because they only have one X. Same with colourblindness
X chromosome becomes randomly inactivated. Why?
- In every single XX combo nucleus, one X chromosome becomes randomly inactivated to avoid over expression. This means even if we’re carriers, some girls can still have the bad allele inactivated and the good one present
What does the hardy Weinberg principle do
predicts proportion of dominant + recessive alleles in a population