Agenda 12/10- Mendelian Genetics

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Agenda 12/10- Mendelian Genetics

• Bellwork (next slide)
• New information Mendelian Genetics
• Finish/discuss Should this dog be called spot?
  worksheet (blocks 1 and 2)
• Punnett Square practice
• HW- finish Punnett Squares, if needed, and
  vocabulary

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Bellwork
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Genetics

• The scientific study of heredity.

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Some vocab

• Trait
• specific characteristic that varies from one
  individual to another
• Gene
• sequence of DNA that codes for a protein and thus
  determines a trait
• Allele
• one of a number of different forms of a gene

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More Vocab!

• The principle of dominance some alleles are
  dominant and others are recessive.
• dominant- expressed even if theres only one
  hides other alleles
• recessive- only shows up if there are two of them
  (homozygous recessive)
• Law of Segregation alleles separate during
  gamete formation so each gamete carries only a
  single copy of each gene (MEIOSIS).

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Gregor Mendel Father of Modern Genetics

• Mendel had true- breeding pea plants.
• He asked the question What would happen if he
  bred pea plants with different traits?

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Dominant and Recessive Traits Gregor Mendels
Peas

• P Parent generation (homozygous)
• F1 first generation of offspring (F filial
  from latin filius son)

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Parent Genotypes- Yellow vs. Green Peas

• The allele gets a letter representing the name of
  the DOMINANT allele (ex. Y for yellow, y for
  green)
• Homozygous two of the same alleles- ex. YY
  homozygous dominant yy homozygous recessive
• Heterozygous two different alleles- ex. Yy

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Punnett Square

• Diagram showing the gene combinations that might
  result from a genetic cross
• Cross YY (female, yellow peas)and yy (male-green
  peas)
• Meiosis produces gametes with only one copy of
  each chromosome, and therefore only one copy of
  each gene. (Law of segregation)

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Probability and Genetics

• Probability - likelihood that a particular event
  will occur

Y Y
y Yy Yy
y Yy Yy
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Genotypes and Phenotypes

• Phenotypes and Genotypes- these plants have
  different genotypes (TT and Tt), but they have
  the same phenotype (tall).
• Genotype genetic makeup
• Phenotype physical appearance

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Crossing true-breeding parent generation

• Trait
• Yellow pea
• dominant
• Genes (alleles)
• YY
• Gametes formed
• Y and Y

P Generation

• Trait
• Green pea
• recessive
• Genes (alleles)
• yy
• Gametes formed
• y and y

Cross YY and yy


Y
Y
F1 Generation
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Crossing the F1 generation

• Trait
• Yellow pea
• Genes (alleles)
• Yy
• Gametes formed

F1 Gen.

• Trait
• Yellow pea
• Genes (alleles)
• Yy
• Gametes formed

Cross Yy and Yy


F2 Generation
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5-minute Write- Punnett Square Practice

• Set up the square for each of the crosses listed
  below. The trait being studied is seed shape
  round seeds (dominant) and wrinkled seeds
  (recessive).
• Rr x rr
• What percentage of the offspring are expected to
  have round seeds? Wrinkled seeds?
• A homozygous round seeded plant is crossed with a
  homozygous wrinkled seeded plant.
• What are the genotypes of the parents?
• What percentage of the offspring will also be
  homozygous?

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• Rr x rr
• What percentage of the offspring will have round
  seeds?
• Wrinkled seeds?

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• A homozygous round seeded plant is crossed with a
  homozygous wrinkled seeded plant.
• What are the genotypes of the parents?
  __________ x __________
• What percentage of the offspring will also be
  homozygous? ____________

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Agenda 12/11/14- Mendelian Genetics

• Bellwork (next slide)
• Dihybrid Crosses
• Practice worksheet
• Homework- Punnett Square practice packet
  vocabulary mini-quiz tomorrow

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Agenda 12/11/14- Mendelian Genetics

• Bellwork (next slide)
• New information Principle of Independent
  Assortment Punnett Square practice
• Homework- vocabulary vocabulary mini-quiz
  tomorrow

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Punnett Square

• Diagram showing the gene combinations that might
  result from a genetic cross
• Meiosis produces gametes with only one copy of
  each chromosome, and therefore only one copy of
  each gene. (Law of segregation)

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Probability and Genetics

• Probability - likelihood that a particular event
  will occur

Y Y
y Yy Yy
y Yy Yy
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Genotypes and Phenotypes

• Phenotypes and Genotypes- these plants have
  different genotypes (TT and Tt), but they have
  the same phenotype (tall).
• Genotype genetic makeup
• Phenotype physical appearance

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Mendels Principles

• Principle of Dominance
• Some alleles are dominant, some are recessive.
• Principle/Law of Segregation
• During meiosis, alleles separate so each gamete
  carries only a single copy of each gene
• Principle of Independent Assortment

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Law of Independent Assortment

• The principle of independent assortment genes
  for different traits can segregate independently
  during gamete formation.
• In other words, genes (alleles) of one trait do
  not affect the inheritance of genes of another
  trait (unless theyre on the same chromosome,
  when they MIGHT be linked).
• This allows us to cross genes for different
  traits at the same time.

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Cross of heterozygous yellow and round peas.

• Dihybrid Crosses (2 traits)
• First, what is the genotype of the parents?
• Second, how many different gametes can be formed?
• Third, what are the different gametes?

Parent RrYy
RY Ry rY ry
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Cross of heterozygous yellow and round peas.

• How many different phenotypes do we expect?
• 4
• What are the expected phenotype ratios?
• 9331

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Agenda 12/12- Mendelian Genetics

• Bellwork- vocabulary quiz (next slide)
• Dihybrid crosses, incomplete and co-dominance,
  multiple alleles, polygenic traits- notes
• Punnett square practice
• HW- finish worksheets, if needed
• Unit test next Thursday (Mendelian Genetics,
  Meiosis)

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Beyond dominant and recessive alleles.

• Most genes do not follow the simple patterns of
  dominant and recessive alleles.
• Some alleles are neither dominant nor recessive,
  and many traits are controlled by multiple
  alleles or multiple genes.

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Beyond dominant and recessive alleles

• Incomplete dominance - one allele is not
  completely dominant over another
• New phenotype blending of the two alleles
• Ex. Red flower, White flower, produce pink flowers

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Beyond dominant and recessive alleles
FRFR

• Incomplete dominance - one allele is not
  completely dominant over another
• New phenotype pink (blending of the two alleles)

FR
FR
FW
FWFW
FRFW
FRFW
FW
FRFW
FRFW
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Beyond dominant and recessive alleles

• Codominance - both alleles of a gene contribute
  to the phenotype of the organism

FB black feathers FW white feathers FBFW
both show equally (black and white feathers) No
blending, as in incomplete dominance.
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Beyond dominant and recessive alleles

• polygenic trait - trait controlled by two or more
  genes
• Ex. Height

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Beyond dominant and recessive alleles

• multiple alleles - three or more alleles of the
  same gene
• Example- human blood type

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Blood Type Inheritance Multiple alleles and
Codominance
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The Human Karyotype
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Agenda 12/15- Autosomal and Sex-linked Traits

• Bellwork
• New information karyotypes, autosomal vs.
  sex-linked traits
• Sex-linked traits worksheet
• Build-a-Kid Lab

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Bellwork 12/15/14

• Determine the possible genotypes of the parents
  and offspring. Brown fur is dominant.
• Two brown dogs are bred and produce 5 puppies, 3
  brown and 2 yellow.
• Two brown dogs are bred, producing 7 brown
  puppies.
• A brown and a yellow dog are bred, producing a
  litter of 3 brown and 2 yellow puppies.

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Question about the HW?
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• How many chromosomes do humans have?
• How many different pairs of chromosomes do humans
  have?

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The Human Karyotype
Homologous Pairs
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Autosomal Dominant and Recessive

• A gene is autosomal if it is on a non-sex
  chromosome.
• A gene is sex-linked if it is found on a sex
  chromosome
• What are the two sex chromosomes?

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Autosomal Disorders

• Autosomal Dominant
• Polydactyly
• Huntingtons Disease
• Brain cells die, nervous system deteriorates
  onset usually between 35-44
• Can a parent be unaffected but pass on the allele
  for the trait to their offspring?

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Autosomal Disorders

• Autosomal Recessive
• Sickle Cell Disease
• Point mutation- affects hemoglobin
• Red blood cells shaped like a sickle (instead of
  a smooth round shape- get stuck in capillaries)
• Whats the advantage?
• Heterozygous individuals have some protection
  from malaria, common in Africa

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Sex-linked Disorders

• Sex-linked disorders are found on sex chromosomes
• Sex-linked recessive traits-
• Females can be carriers- have one allele for the
  trait but do not express it.
• Males either have the disorder or dont. They
  cant be carriers.

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Sex-linked Disorders

• Red-Green Colorblindness
• Sex-linked recessive
• 5-10 of males affected
• Cross a heterozygous female with a homozygous
  dominant male

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• Cross a heterozygous female with a homozygous
  dominant male.

• Probability that a child will be female?
• Probability that a child will be male?
• Probability that a female child will be
  color-blind?
• Probability that a male child will be
  color-blind?
• Why are males more likely to be color-blind?

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Sex-linked Traits Practice

• Complete the worksheet in pairs.
• When youre done, check in with me and get the
  Build a Kid Lab

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Bellwork 12/16
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Agenda 12/16- Nondisjuction Pedigrees

• Bellwork
• Review sex-linked traits worksheet
• New information nondisjunction pedigrees
• Build a Kid Lab
• HW- finish review worksheet, study for test
  Thursday

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The Human Karyotype
Homologous Pairs
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Chromosomal Abnormalitites

• Sometimes there are errors during meiosis, and
  chromosomes dont divide correctly
  (nondisjunction).
• Karyotyping can be used to predict genetic
  disorders.
• Trisomy 21- Downs Syndrome
• 3 copies of chromosome 21

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Other Chromosomal Disorders

• Sex Chromosomes (23)- X, Y
• XX or XY
• Turner Syndrome
• monosomy (one copy) 23
• XO
• Klinefelter Syndrome
• Trisomy 23
• XXY

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Pedigrees

• Pedigree family tree

Affected male
Affected female
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Pedigree

• Draw a pedigree for the following family.
• Jane and Pete are married. They have 2 children
  one boy and one girl.
• Their daughter, Joan, is married to Dale, and
  they have one daughter.
• Jane and Petes son is married to Debbie, and
  they have 4 children 3 boys and one girl.
• Pete, Joan, and the Dales daughter all have an
  autosomal recessive disease.

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Hemophilia A the Royal Disease
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X-Linked Cross

• Hemophilia A a hereditary blood disorder,
  primarily affecting males (1 in 10,000) and
  rarely affecting females (1 in 100,000,000).
• Characterized by a deficiency of the blood
  clotting protein that results in abnormal
  bleeding.
• Hemophilia is a recessive genetic disorder
  located on the X chromosome (sex-linked trait).

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Hemophilia A the Royal Disease
Alice of Athlone, had one hemophilic son (Rupert)
and two other childrena boy and a girlwhose
status is unknown. a) What is the probability
that her other son was hemophilic? b) What is the
probability that her daughter was a carrier? A
hemophiliac? c) What is the probability that both
children were normal?
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Summary of Mendels Principles

• Genes code for proteins, and therefore traits,
  and are passed from parents to their offspring
  (heritable).
• Principle of Dominance When two or more forms of
  the gene for a single trait exist, some forms of
  the gene may be dominant and others may be
  recessive.
• In most sexually reproducing organisms, each
  adult has two copies of each geneone from each
  parent. These genes are segregated (usually
  independently) from each other when gametes are
  formed. (Independent Assortment, Law of
  Segregation)

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Linkage and Gene Maps

• Which law states that genes located on different
  chromosomes separate independently?
• But what about genes located on the same
  chromosome?
• Wouldnt they generally be inherited together?
• Thomas Hunt Morgans studies back in 1910 helped
  us to answer this question.

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Linkage and Gene Maps

• Just because two genes are located on the same
  chromosome does not mean that they are linked
  together forever.
• Crossing-over (metaphase I of meiosis I)
• The further apart the genes are the more likely
  they are to separate. The closer they are the
  less likely they are to separate.