Mendilian Genetics Flashcards
what is Mendelian genetics
elementary aspects of inheritance in organisms with more than one chromosome
who is the father of genetics
Gregor Mendel
How was Mendelian genetics discovered and when
in 1800’s
studied peas
looked at 7 discrete traits of peas
two main types of genetic expirments
monohybrid cross
dihybrid cross
Phenotype
what you see in an organism (purple flower)
genotype
all the alleles in an organism (recessive an dominant traits)
F1
results of e genetic cross between parents (filial generation)
F2
second filial generation
Homozygous
alleles are identical, both dominant or both recessive (AA or aa)
Heterozygous
alleles are different one dominant and one recessive (Aa)
Dominant
allele that is seen (expressed in phenotype when heterozygous)
Recessive
allele that isn’t seen (expressed on phenotype when heterozygous)
Ratio when you cross F1 x F1 monohybrid
3:1
Ratio when you cross F1 x F1 dihybrid
9:3:3:1
test cross
cross an unknown genotype with a known genotype
Mendel’s first law of segregation
-Alleles of the same gene segregate independently from one another during the formation of gametes
2 ways Mendel’s first law works
-genes on different chromosome’s end up with different gametes
-crossing over
Mendel’s second law of segregation
separate genes for separate traits are passed independently of one another from parents to offspring
autosomal
not sex-linked
autosomal dominant
if you have the gene you have the disease
autosomal recessive
if you have the gene it only shows up if you are homozygous for it (aa)
also known as a carrier
recombination (3)
-Alleles linked on the same chromosome exchange segments between homologous chromosomes
-Exchanges occur while homologous chromosomes pair during Prophase 1
-The farther apart the genes are the more likely they are to go through recombination
Gene Linkage
-Amount of recombination between two genes reflects the distance between them
how is the location of a gene measured
map units
1 map unit =
1%
how many map units apart can chromosomes be
50 or else they are on different chromosomes
how is gender determined
SRY gene
Pedigree
a chart that shows genotypes and phenotypes in a family’s past generations
Dosage Compensation
Females all have one X-chromosome that is active and one that is inactive
Barr Bodies
The random X chromosome that is inactivated
What is the same in all female descendants
The x chromosome that is inactivated
Why are all calico cats female
The colour gene is on the x chromosome and if both the colour orange and black are on it there are no other chromosomes to block out both colours
What are Trisomies
Mutation in the X and Y chromsomes
Turners syndrome and characteristics of it
Female with only 1X chromosome
-Short especially arms and neck
-Can’t reproduce
Kleinfelder’s syndrome and characteristics
Having 2 X-chromosomes and 1 Y
-Pheno and Geno male
-Lots of head hair
-Breast enlargement
-reduced muscle mass
Down syndrome and characteristics
3 copies of gene 21
-Developmental delay
-very happy
-Can’t live independently
Jacobs syndrome and characteristics
1 X-chromosome and 2 Y-chromosomes
-Double does of testosterone
-Super strong
Codominance and example
A genetic inheritance pattern where two alleles of a gene are expressed equally resulting in different traits
-Blood type
LDL
Low density Lipoproteins
How many LDL receptors do Homozygous Dominant have
Many
How many LDL receptors does a Heterozygous have
half of a homo dominant
How many LDL receptors does a Homozygous recessive have
None
Polygenic Inheritance
Inheritance where multiple genes control the trait, which is why we don’t have the same skin colour or height as our parents
Epistatis and example
The expression of one gene depends on the presence of one or more modifier genes
Ex: eye colour, you could have the gene to give you green eyes, but if you have the gene for brown eyes because the brown pigment overwhelms the green pigment.
Non-Nuclear Inheritence
Comes through the mitochondria which is inherited from your mother. So if your mother is affect you
Example of environmental effects
The warmer part of a Siamese cat have less colour then the cooler part of the cat like the ears and tail which are darker.
In a dihybrid cross what is the typical phenotypes) of the F1 generation if P1 is RRhh and P2 is rrHH
3RrHh: 1rrhh
The alleles of a gene
-The observable characteristics of an organism determined by genetic composition
-The combination of alleles located at a specific location on homologous chromosomes that determine a trait of an organism
Any of the alternative forms of a gene or homologous sequence of DNA
-The trait in the organism
-None of the above
The observable characteristics of an organism determined by genetic composition
In a test cross the parents are always an unknown genotype and a known genotype. What is the genotype of the known parent?
Homologous recessive
In a monohybrid cross, the parents have the genotype Rr and rr. What proportion of the F1 will be homozygous recessive
25%
If a characteristic is autosomal, what does this mean?
The gene is not located on the sex chromosomes
