53 Cards in this Set
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What is genetics?
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The study of the mechanisms of:
-hereditary transmission (individual)
-the variation of inherited characteristics (population)
among organisms
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Genome
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A complete set of the genetic information of an orgaism
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Chromosome
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a linear molecule of DNA
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Gene
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A gene is a piece of DNA corresponding to a unit of inheritance
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What do genes do?
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1. relpicate and pass on genetic information
2. Encode for and make proteins
3. Occasionally genes will mutate and generate diversity
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How is a DNA molecule combinded into its 3D structure?
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1. spooling
2.coiling
3.looping
4. supercoiling
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Allele
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alternate forms of a gene on the same chromosome
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Centromere
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the region of the chromosome to which spindle fibers attach in a dividing cell
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What are the three possible locations of a centromere on a chromsome?
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telocentric - at the end of a chromosome
acrocentric - off center
metacentric - in the middle
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Telomere
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Repeated DNA sequence at the ends of chromosomes
As individuals age telomeres are gradually lost
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What are the two genetic approaches to biological research?
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Foward genetics
reverse genetics
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Forward genetics
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Mutation→ gene discovery → DNA sequence and function
A mutation occurs which leads to research being done as to what gene caused it and what that gene's sturcture and function is
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Reverse genetics
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DNA sequence of a gene→ mutation→function
A DNA sequence is isolated and removed or changed. The mutation that occurs is observed leading to the discovery of that gene's function.
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The migration of homo sapiens was able to be tracked over time using which two pieces of the human body/genome?
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mitochondria (women)
Y chromosome (men)
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Phenotypes
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chanracteristics that you can see
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Who is considered the father of genetics?
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Gregor Mendel
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What are the two methods of fertilization used by Mendel?
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cross pollination- when the pollen of one plant is transfered to the stigma of another
Selfing- when the pollen of one plant is transfered to its own stigma
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How did Mendel test his hypothesis that some parents carried genes that were not expressed but they passed them on to their offspring?
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He created two pure lines one with the dominant phenotype and one with the recessive. He crossed these two plants and the F1 generation did not show any recessive phenotype but when the F1 generation was selfed the recessive phenotype reappeared in the F2 generation. This showed that it r…
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In a monohybird cross where both parents are heterozygous what are the genotypic and phenotypic ratios of the offspring produced?
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Genotypic 1 homozygous dominant: 2 heterozygous: 1 homozygous recessive 1:2:1
Phenotypic- 3 dominant phenotype: 1 recessive phenotype 3:1
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Mendel's first law
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the law of equal segregation- the two members of a gene pair (alleles) segregate from each other into the gametes; so half the gametes carry one member of the pair and the other half carries the other member
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Monohybird cross
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a single trait is being followed
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Dihybrid cross
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to traits are eing followed
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At what stage of Meiosis does crosing over occur?
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Metaphase 1.
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Chiasma
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the pint where two homolgous non-sister chromatids exchange genetic material (where crossing over occurs)
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What are some differences between mitosis and meiosis?
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Mitosis -
creates two daughter cells that are identical to the mother cell
Meiosis-
creates 4 daughter cells each with half the number of chromosomes as the original cell
experiences synapsis in the prophase 1 when two chromosome pairs group together
goes th…
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Barr bodies
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Barr bodies are condensed inactive X chromosomes. All but one X chromosome has a barr body
- normal males have none
- normal females have 1
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Meiosis generates variation through which two processes?
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1. Recombination- crossing over
2. independent assortment
-chromosomes from the same parent are not inherited as a block
- genes on seperate chromosomes are inherited independently
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What are the 3 mechanisms of sex determiantion?
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1. Genic mechanisms (usually prokaryotes)
2. Chromosomal mechanisms
3. Environmental sex determination systems
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What are the three patterns of chromosomal sex determination mechanisms?
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1. XY- Female XX male XY (males determine gender)
2. XO- Female XX male X
3. ZW- Female ZW male ZZ (female determines gender)
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Incubation temperature determining sex is an example of which mechanism of sex determination?
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Environmental
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What part of the Y chromosome causes it to result in male offspring?
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SRY (maleness) gene
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What does the SRY gene do?
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- inhibits production of p450 aromatase which converts the male hormone testosterone, to the female hormone estradiol → male
- enhances a gene which promotes testicle development and represses female reproductive structures → male
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What is the phenotypic ratio that would result from a cross of R/R; y/y and r/r; Y/Y for pea shape and color? R= round r= wrinkled, Y= yellow y=green
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9:3:3:1
9 round yellow: 3: wrinkled yellow: 3 round green: 1 wrinkled green
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What are the genotypes of the parents in a dihybrid testcorss? (use R and Y alleles)
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R/r; Y/y and r/r; y/y
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what is the phenotypic and genotypic ratio that results from a dihybrid testcross?
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1:1:1:1
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What is Mendel's second law?
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The law of independent assortment-
gene pairs on differnt chromosome pairs assort independently at meiosis
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How do you predicting the number of genotypes that will be possible in any given cross?
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number of tenotypes = 3n where n= the number of traits being observed.
in a trihybird cross n=3 so 33= 27 possible genotypes
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How do you predict the number of phenotypes that can be expected with any given cross?
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number of phenotypes = 2n where n= the number of traits being observed
in a trihybrid cross n= 3 so 23= 8 possible phenotypes
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Independent assortment produces _____ recombinants.
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50%
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Population
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A local group within which interbreeding is more common than with other groups
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What are the 3 types of variation
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1. allelic
2. genotypic
3. phenotypic
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What are the assumptions required for the hardy-weinberg equilibrium?
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- no migration
- no mutation
- infinitely large population
- mating is random
- no natrual selection
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What is the chi square equation?
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x2= ∑ (oserved- expected)2/ expected
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positive assortive mating
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mating with like partners
leads to an excess in homozygotes
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negative assortive mating
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mating with unlike partners
leads to an increase in heterozygotes
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what are two adverse consequences of inbreeding
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-inbreeding depression- increase in frequency of certain traits
- emergance of harmful trait
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Which produces variation faster mutation or recombination?
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recombination
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What are three factors that contribute to the rapid emergence of antibiotic resistance in bacterial pathogens?
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1. short generation times and high rate of reproduction
2. Large population density
3. Srong selection imposed by antibiotics
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Domestication bottleneck
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When plants and animals were domesticated they were bred for certian desirable traits. Because many traits were bred out a sort ob bottleneck occured where the gene pool was greatly decreased.
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Stabilizing selection
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Selection that leads away from extremes. generally leads to more heterozygotes
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Migration
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any introduction of genes from one population to another
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Genetic Drift
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random changes in allele frequencies from generation to generation
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Does random genetic drift have a greater effect in large or small populations?
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small. In large populations with large and diverse gene pools the change in an allele will not make much of a difference but when a population is small even a single change will cause a greater change to the gene pool.
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BIOL 240: Exam 1