Genetics Notes Flashcards
History of Genetics
- 1800’s: Blending……wrong!
- Modern Genetics: Particulate
Modern Genetics: Particulate
- Monogenic Inheritance
- Cytogenetics
- Multifactorial
Monogenic Inheritance
- Dominant, recessive, x-linked
- Easy to understand and solved with a Punnett Square, but very rare
Cytogenetics
Karyotype used to visualize, easy to understand, but rare
Multifactorial
- Common conditions but complex genetic traits
- Must understand entire genome and look for variants
- People are 99.6% the same
- Common variants = common diseases
- Quantatative Traits
Who is Gregor Mendel
- His experiments-> bred 2 pea plants-> one tall and one short and found 3/4 offspring tall and 1/4 short.
- Discovered within genes dominant and recessive alleles
- 7 traits in pea plants
- Why pea plants? T
Genetics
Studying hereditary patterns through the use of genes and how they are expressed
F1 and F2 Generations
Parent tree cross and the offspring is F1 and two F1s cross to make F2
Reginald Punnett (Mendel Statistics)
Made punnette square
Chromosome vs. Gene
-Chromosome-> coiled up strand of DNA, the whole strand. Contains genes
Genes-> a certain section of DNA that codes for certain allels
Alleles
Make up genes and codes for certain traits
Dominant vs. Recessive
- When dominant is present with recessiv (Aa), only dominant is expressed
- Dom is capital, recessive is lowercase
Homozygous vs. Heterozygous
Homozygous-> two dominants or two recessives that code for the same thing. (AA or aa). If homozygos dominant, dom trait is expressed, if homozygous recessive, recessive shows up. Same types of alleles
Heterozygous- A dominant and a recessive show up in genotype, but only dominant is expressed. Dif types of alleles
Genotype vs. Phenotype
Genotype-Gene combo (Aa)
Phenotype- What physical trait shows up- (black hair)
From gene to trait
From DNA-> (transcription) RNA-> (translation)-> Protein -> trait
What can Karyotypes tell us? What can it
not tell us?
Can: gender, genetic disorders
Can’t- what look like
Genetics Problem Rules
- Assign letters to represent the alleles: Cap for dom, lower case for rec
- Read problem for parent genotye. If heterozygous, cap letter first
- Solve problem with punnette square
- You must always..
Genetics Problem Rules: you must always…
- Have a key for the letters
- Show the genotypes of the parents
- Show your work in a Punnett Square
- Answer what the question is asking
Monohybrid Crosses
Involves a single gene where one allele is dominant over another - Use an upper and lower case letter T=Tall t=short
Incomplete Dominance
Involves a single gene where neither trait is dominant over
another. Results in an intermediate expression of the trait
- Use two upper case letters
R=Red
W=White
Dihybrid Crosses
-Involves two genes rather than one
-Follow the rules given in the problem, may be complete or incomplete
T=pointed wings P=pink wings
t=rounded wings p=yellow wings
TT or Tt
PP or Pp
TtPp
ttpp
Sex-linked Traits
- Involves genes on the X sex chromosome
- First discovered in the early 1900’s by Thomas Hunt Morgan who was studying fruit flies.
- Most sex-linked genes are recessive which means it only takes one gene from the mother to give the male offspring (XY) the mutant trait. Females (XX) need two genes, one from each parent to have the mutant trait.
- Carrier Females: females who carry a recessive allele but do not have the recessive phenotype
Multiple Alleles
-Involves a single trait that is controlled by 3 alleles (rather
than 2 which is what we are used to)
- Blood types are the most common example, O is
recessive, but A and B are both dominant
- Alleles: A, B, O
Epistasis
- Involves a single trait, but two genes at different loci on a single chromosome
- Loci is the location of the gene on a chromosome
- One gene controls the trait while the other turns the first gene on or off depending on the genotype.
Pedigress
- A chart used to track traits through generations
- Females are circles, Males are squares
- Shaded individuals show a trait (usually recessive)
- Generations are given roman numerals
- Individuals in generations are given numbers
Mutations
-Random changes in a genome that occur during cell division and/or reproduction
Evolution
-Random process controlled by mutations
Natural Selection:
- Nonrandom process controlling populations
Hardy-Weinburg
- Equilibrium
- If everything in population stays the same, then nothing the population will change
Gene Pool
-All the different genes/alleles in an area/population
Gene Frequency
-Gene percentage of how alleles are consistent or appear in the population
Does natural selection always choose against the recessive trait
No, not always, it goes against the weaker gene. EX: dominant gene is getting killed off but recessive survives
