gregory mendel gregory developed own experiment to study different traits in _____ first scientist...
TRANSCRIPT
Gregory Mendel• Gregory developed own
experiment to study different traits in _____
• First scientist to study genetics
• “_________________”
_________• Units of information about specific traits
• Passed from _______ to _________
• Each has a specific___________(locus) on a chromosome
___________
• Different forms of a gene
• Each person has _____ alleles for each trait
• 2 types
• ________ (A)
• ________ (a)
Must KNOW Vocabulary!_____________-transmitted from one generation to
the next, contains many genes
__________- sequence of DNA on the chromosome, determines trait (about 30,000 in humans)
_________-alternative forms of a gene
More Vocab……• ____________- 2 copies of allele are the same
– _____
– _____
• _____________- 2 copies of allele are different
– ______
And more Vocab…..
•___________- what you see
•(___________)
•__________- actual alleles present
•(________)
Probability• The chance that an outcome of a given event
will occur
• _________________give probability for what kinds of offspring will be born…..doesn’t tell _______ how many of each kind you will have
• EX: if you flip a coin
10 times, you would
predict 5 heads/5 tails.
• Is this always true???
Punnett-Square Method• Draw a box
• Put genotype at the top, bring alleles down
• Put other genotype on the side, bring alleles over
___________• Write lines for all of your individuals
• Put in known alleles
• Work backwards to solve to missing alleles
Tracking Generations• Parental generation (_____)
• First-generation offspring (______)
• Second-generation offspring (______)
Mendel’s Second Law:___________________________
____________• Traits don’t always stay
together
• EX: white/short tail
• Brown/long tail
Aren’t inherited together!
Dihybrid Crosses
• Always use to compare the possibility of inheriting 2 different traits– Figure out genotypes of parents– Find all possible allele combinations for their
gametes• F.O.I.L.- firsts, outers, inners, lasts
– Complete a Punnett Square to solve for offspring
Question of the Day
• Brown eyes are dominant to blue eyes
• Freckles are dominant to no freckles
• Mom is heterozygous
• Dad is heterozygous
Epistasis
•One gene can mask the phenotypic effects of a different gene
– Results when more than one gene codes for a particular trait
– Common among genes for hair color in mammals
• Black B is dominant to brown b– BB Black– Bb Brown
• Yellow the epistasis trait that is only present when homozygous recessive – BE black– bE brown– Ee yellow
Pleiotropy
• Alleles at a single locus may have effects on two or more traits– Eye color– Skin color
• A rose breeder finds that when he crosses a true-breeding climber with a true-breeding shrubby plant all F1 offspring are climbers. Find the F2 generation.
• He also found that when he crossed sweet smelling roses with no scent roses, all of the F1 plants smelled sweet. Find the F2 generation.
• Using the information from above cross a plant that is hetero for BOTH traits with a plant that is hetero for BOTH traits. What does your F1 generation look like?
Incomplete Dominance
• a cross between individuals with two different phenotypes produces offspring with a third phenotype that is different
• Heterozygous genotype displays a different phenotype than either homozygous parent
Codominance
• a cross between two different phenotypes produces offspring with a third phenotype in which both of the parental traits appear together.
• Heterozygous produces phenotype with both parent’s phenotypes visible
• Blood Typing
• Thorns on roses are controlled by 2 genes. Thorns are dominant to no thorns for the first gene. However the other gene will overshadow the first and will show the phenotype of thorns if a dominant allele is present.
• Solve the phenotypes of the offspring if one plant that is hetero for both genes crosses with another plant that is homoz recessive for both genes.
• Solve for the possible parents genotypes if there are 3 offspring in the F1 generation, 2 that do not have thorns and the other does have thorns.
• If you cross a homoz red plant with a white plant all F1 offspring are pink. However if you cross homoz tall plant with a homoz short plant all F1 offspring are tall.
• You cross a hetero tall, pink plant with a short, white plant. What are the genotypes and phenotypes of the offspring?
• Identify the parents if you haveF1 offspring that are tall/red, short/pink.
• What would you cross with a hetero tall pink plant to get offspring that are short and pink? Justify your answer.
Blood Types
• Gene that controls ABO type codes for enzyme that dictates structure of a glycolipid on blood cells
• Two alleles (IA and IB) are codominant when paired
• Third allele (i) is recessive to others
Blood Transfusions
• Recipient’s immune system will attack
blood cells that have an unfamiliar
glycolipid on surface
• Type O is universal donor because it has
neither type A nor type B glycolipid
48.Mom is type A and has a child that is type O, what is/are dads possible blood type/s?
49.If mom is hetero type B and dad is hetero A, what is/are the possible blood types of the offspring going to be?
50.Which blood type is recessive to the other types?
Answers:a. Type A, Type B, Type ABb. Type A, Type B, Type Oc. Type ABd. Type Oe. All of these
Linkage and Cross-over
• Each chromosome becomes zippered to
its homologue
• All four chromatids are closely aligned
• Non-sister chromosomes exchange
segments
Effects of Crossing Over
• After crossing over, each chromosome
contains both maternal and paternal
segments
• Creates new allele combinations in
offspring
Linkage Groups
1. Two or more genes can be located on the same chromosome
2. Genes that are close together tend to be transmitted as a unit but not all genes are transmitted together
Crossover Frequency
• Proportional to the distance that separates Proportional to the distance that separates genesgenes
Pedigree Analysis• Genetic Abnormality: A rare uncommon version
of a trait
– polydactyly
• Genetic Disorder: Inherited conditions that cause mild to severe medical problems
– Why don’t they disappear?
• Mutation introduces new rare alleles
• In heterozygotes, harmful allele is masked,
so it can still be passed on to offspring
Phenotypic Treatments
• Symptoms of many genetic disorders can
be minimized or suppressed by
– Dietary controls
– Adjustments to environmental conditions
– Surgery or hormonal treatments
Genetic Screening
• Large-scale screening programs detect affected persons
• Newborns in United States routinely tested for PKU– Early detection allows dietary intervention and
prevents brain impairment
Prenatal Diagnosis
• Amniocentesis
• Chorionic villus sampling
• Fetoscopy
• All methods have some risks
Preimplantation Diagnosis
• Used with in-vitro fertilization
• Mitotic divisions produce ball of 8 cells
• All cells have same genes
• One of the cells is removed and its genes
analyzed
• If cell has no defects, the embryo is
implanted in uterus
Karyotype Preparation:
• Stopping the Cycle:– Cultured cells are arrested at metaphase by
adding colchicine– This is when cells are most condensed and
easiest to identify
Karyotype Preparation
• Arrested cells are broken open
• Metaphase chromosomes are fixed and stained
• Chromosomes are photographed through microscope
• Photograph of chromosomes is cut up and arranged to form karyotype diagram
Chromosome Structure
• Alterations to chromosome structure are usually bad
• Duplications are adaptive: one gene functions normally - the other is free to mutate
• Chromosome structure evolves
Aneuploidy
• Individuals have one extra or less chromosome
• (2n + 1 or 2n - 1)
• Major cause of human reproductive failure
• Most human miscarriages are aneuploids
Polyploidy
• Individuals have three or more of each type of chromosome (3n, 4n)
• Common in flowering plants
• Lethal for humans– 99% die before birth
– Newborns die soon after birth
Duplication• Gene sequence that is repeated several to
hundreds of times
• Duplications occur in normal
chromosomes
• May have adaptive advantage
– Useful mutations may occur in copy
Translocation• A piece of one chromosome becomes
attached to another nonhomologous chromosome
• Most are reciprocal