Chapter 5B

Gregor Mendel Famous pea plant study Famous pea plant study Mendelian genetics Mendelian genetics “Father of Genetics” “Father of Genetics” Famous pea plant study Famous pea plant study Mendelian genetics Mendelian genetics “Father of Genetics” “Father of Genetics”

Father of Genetics  Monk and teacher.  Experimented with purebred tall and short peas.  Discovered some of the basic laws of heredity.  Studied seven purebred traits in peas.  Called the stronger hereditary factor dominant.  Called the weaker hereditary factor recessive.  Presentation to the Science Society in1866 went unnoticed.  He died in 1884 with his work still unnoticed.  His work rediscovered in  Known as the “Father of Genetics”.  Monk and teacher.  Experimented with purebred tall and short peas.  Discovered some of the basic laws of heredity.  Studied seven purebred traits in peas.  Called the stronger hereditary factor dominant.  Called the weaker hereditary factor recessive.  Presentation to the Science Society in1866 went unnoticed.  He died in 1884 with his work still unnoticed.  His work rediscovered in  Known as the “Father of Genetics”.

Mendelian Genetics Began with 34 varieties of pea seeds Began with 34 varieties of pea seeds Chose 7 sets of opposing characteristics Chose 7 sets of opposing characteristics Chart, page 113 Chart, page 113 Began with 34 varieties of pea seeds Began with 34 varieties of pea seeds Chose 7 sets of opposing characteristics Chose 7 sets of opposing characteristics Chart, page 113 Chart, page 113

Mendel’s Peas Mendel’s Peas

Self-pollination vs. Cross-pollination Self-pollination vs. Cross-pollination

Mendel’s Observations  He noticed that peas are easy to breed for pure traits and he called the pure strains purebreds.  He developed pure strains of peas for seven different traits (i.e. tall or short, round or wrinkled, yellow or green, etc.)  He crossed these pure strains to produce hybrids.  He crossed thousands of plants and kept careful records for eight years.  He noticed that peas are easy to breed for pure traits and he called the pure strains purebreds.  He developed pure strains of peas for seven different traits (i.e. tall or short, round or wrinkled, yellow or green, etc.)  He crossed these pure strains to produce hybrids.  He crossed thousands of plants and kept careful records for eight years.

Mendel’s Peas  In peas many traits appear in two forms (i.e. tall or short, round or wrinkled, yellow or green.)  The flower is the reproductive organ and the male and female are both in the same flower.  He crossed pure strains by putting the pollen (male gamete) from one purebred pea plant on the pistil (female sex organ) of another purebred pea plant to form a hybrid or crossbred.  In peas many traits appear in two forms (i.e. tall or short, round or wrinkled, yellow or green.)  The flower is the reproductive organ and the male and female are both in the same flower.  He crossed pure strains by putting the pollen (male gamete) from one purebred pea plant on the pistil (female sex organ) of another purebred pea plant to form a hybrid or crossbred.

Mendel’s Results Mendel crossed purebred tall plants with purebred short plants and the first generation plants were all tall. When these tall offspring were crossed the result was a ratio of 3 tall to 1 short.

Mendel’s Experiments  He experimentally crosses different strains to develop hybrids.  He then crossed the hybrids and analyzed the results.  He experimentally crosses different strains to develop hybrids.  He then crossed the hybrids and analyzed the results.

Dominant Traits RULE Strong Hereditary traits cover weak traits. Strong Hereditary traits cover weak traits. Mendal called stronger traits Mendal called stronger traits DOMINANT DOMINANT Mendal called weaker traits Mendal called weaker traits recessive recessive Strong Hereditary traits cover weak traits. Strong Hereditary traits cover weak traits. Mendal called stronger traits Mendal called stronger traits DOMINANT DOMINANT Mendal called weaker traits Mendal called weaker traits recessive recessive Dominant traits are represented by capital letters (T) while recessive traits are represented by lower case letters (t). try and follow the diagram on the next slide while keeping the DOMINANT and recessive letters in mind. ( TT) (tt ) Dominant traits are represented by capital letters (T) while recessive traits are represented by lower case letters (t). try and follow the diagram on the next slide while keeping the DOMINANT and recessive letters in mind. ( TT) (tt )

In the diagram above, the dominant allele is represented by ___and the recessive allele is represented by __.

Mendelian Genetics P 1 : the original parent generation P 1 : the original parent generation F 1 : first filial generation; offspring of the P 1 generation F 1 : first filial generation; offspring of the P 1 generation F 2 : second filial generation; offspring of the F 1 generation F 2 : second filial generation; offspring of the F 1 generation P 1 : the original parent generation P 1 : the original parent generation F 1 : first filial generation; offspring of the P 1 generation F 1 : first filial generation; offspring of the P 1 generation F 2 : second filial generation; offspring of the F 1 generation F 2 : second filial generation; offspring of the F 1 generation

If we consider your parents to be the P 1 generation, which generation are you? 1. P 1 1. P 1 2. P 2 2. P 2 3. F 1 3. F 1 4. F 2 4. F 2 1. P 1 1. P 1 2. P 2 2. P 2 3. F 1 3. F 1 4. F 2 4. F 2

The concept of unit characteristics Factors occur in pairs.

Genes occur in pairs because diploid organisms have 1. daughter chromosomes. 1. daughter chromosomes. 2. homologous pairs of chromosomes. 2. homologous pairs of chromosomes. 3. gametes. 3. gametes. 1. daughter chromosomes. 1. daughter chromosomes. 2. homologous pairs of chromosomes. 2. homologous pairs of chromosomes. 3. gametes. 3. gametes.

The concept of dominant & recessive

Dominant Traits RULE Strong Hereditary traits cover weak traits. Strong Hereditary traits cover weak traits. Mendal called stronger traits Mendal called stronger traits DOMINANT DOMINANT Mendal called weaker traits Mendal called weaker traits recessive recessive Strong Hereditary traits cover weak traits. Strong Hereditary traits cover weak traits. Mendal called stronger traits Mendal called stronger traits DOMINANT DOMINANT Mendal called weaker traits Mendal called weaker traits recessive recessive Dominant traits are represented by capital letters (T) while recessive traits are represented by lower case letters (t). try and follow the diagram on the next slide while keeping the DOMINANT and recessive letters in mind. ( TT) (tt ) Dominant traits are represented by capital letters (T) while recessive traits are represented by lower case letters (t). try and follow the diagram on the next slide while keeping the DOMINANT and recessive letters in mind. ( TT) (tt )

Dominant trait A trait that is expressed and masks the expression of the other trait A trait that is expressed and masks the expression of the other trait Examples on page 113 Examples on page 113 A trait that is expressed and masks the expression of the other trait A trait that is expressed and masks the expression of the other trait Examples on page 113 Examples on page 113

Recessive trait A trait which, when in the presence of a dominant trait, is not expressed A trait which, when in the presence of a dominant trait, is not expressed

Capital letters (T) = dominant Capital letters (T) = dominant Lowercase letters (t) = recessive Lowercase letters (t) = recessive A, a; B, b; R, r; etc. A, a; B, b; R, r; etc. Capital letters (T) = dominant Capital letters (T) = dominant Lowercase letters (t) = recessive Lowercase letters (t) = recessive A, a; B, b; R, r; etc. A, a; B, b; R, r; etc. Language of Genetics Problems

The concept of segregation

A cell forms gametes during which process? 1. Mitosis 1. Mitosis 2. Meiosis 2. Meiosis 3. Cytokinesis 3. Cytokinesis 4. Fertilization 4. Fertilization 1. Mitosis 1. Mitosis 2. Meiosis 2. Meiosis 3. Cytokinesis 3. Cytokinesis 4. Fertilization 4. Fertilization

Monohybrid cross A genetic cross dealing with only one set of characteristics A genetic cross dealing with only one set of characteristics Punnett square A diagram used to show the possible gamete combinations from a genetic cross A diagram used to show the possible gamete combinations from a genetic cross

PUNNETT SQUARE CROSS T T X Tt

CONT’D T T X T t T T T t T TTT TtTt

Allele Types Homo - Same Homo - Same Hetero - Opposite Hetero - Opposite Pheno – Physical Pheno – Physical Geno - Genetic Geno - Genetic Homo - Same Homo - Same Hetero - Opposite Hetero - Opposite Pheno – Physical Pheno – Physical Geno - Genetic Geno - Genetic

Phenotype The physical expression of an organism’s genes The physical expression of an organism’s genes Examples: tall, short, black Examples: tall, short, black The physical expression of an organism’s genes The physical expression of an organism’s genes Examples: tall, short, black Examples: tall, short, black Genotype The genetic make-up of an individual; the genes it has The genetic make-up of an individual; the genes it has Examples: Tt, AA, bb Examples: Tt, AA, bb The genetic make-up of an individual; the genes it has The genetic make-up of an individual; the genes it has Examples: Tt, AA, bb Examples: Tt, AA, bb

Homozygous When both alleles in a cell are the same When both alleles in a cell are the same Examples: tt, TT, BB, bb Examples: tt, TT, BB, bb When both alleles in a cell are the same When both alleles in a cell are the same Examples: tt, TT, BB, bb Examples: tt, TT, BB, bb Heterozygous When both alleles in a cell are NOT the same When both alleles in a cell are NOT the same Examples: Bb, Tt Examples: Bb, Tt When both alleles in a cell are NOT the same When both alleles in a cell are NOT the same Examples: Bb, Tt Examples: Bb, Tt

Locus The site on a chromosome where a particular gene is located The site on a chromosome where a particular gene is located Allele One of a pair of genes that has the same position on homologous chromosomes One of a pair of genes that has the same position on homologous chromosomes Examples: T or t Examples: T or t One of a pair of genes that has the same position on homologous chromosomes One of a pair of genes that has the same position on homologous chromosomes Examples: T or t Examples: T or t

Gene Expression Are the following sentences true or false? - Homozygous organisms are true breeding for a particular trait. False False - Plants with the same phenotype always have the same genotype. False False Are the following sentences true or false? - Homozygous organisms are true breeding for a particular trait. False False - Plants with the same phenotype always have the same genotype. False False

Probability In Mendel’s model of segregation, what was the ratio of tall plants to short plants in the F2 generation? In Mendel’s model of segregation, what was the ratio of tall plants to short plants in the F2 generation? The ratio was 3 : 1. The ratio was 3 : 1. In Mendel’s model of segregation, what was the ratio of tall plants to short plants in the F2 generation? In Mendel’s model of segregation, what was the ratio of tall plants to short plants in the F2 generation? The ratio was 3 : 1. The ratio was 3 : 1.

Incomplete Dominance

Both alleles are expressed, but neither one is dominant. Both alleles are expressed, but neither one is dominant. KEY: a blending of the traits KEY: a blending of the traits Example: Example: When red snapdragons are crossed with white snapdragons, the resulting offspring are pink. When red snapdragons are crossed with white snapdragons, the resulting offspring are pink. Both alleles are expressed, but neither one is dominant. Both alleles are expressed, but neither one is dominant. KEY: a blending of the traits KEY: a blending of the traits Example: Example: When red snapdragons are crossed with white snapdragons, the resulting offspring are pink. When red snapdragons are crossed with white snapdragons, the resulting offspring are pink.

1st generation CwCw CwCw CwCw CwCw CrCr CrCr CrCr CrCr CrCwCrCw CrCwCrCw CrCwCrCw CrCwCrCw CrCwCrCw CrCwCrCw CrCwCrCw CrCwCrCw

2nd generation Phenotypic: _________ Phenotypic: _________ CrCr CrCr CwCw CwCw CrCr CrCr CwCw CwCw CrCrCrCr CrCrCrCr CrCwCrCw CrCwCrCw CrCwCrCw CrCwCrCw CwCwCwCw CwCwCwCw Genotypic: _________ Genotypic: _________ 1 : 2 : : 2 : 1

Human example Brachydactyly Brachydactyly

Codominance Two alleles for a gene are both expressed. Two alleles for a gene are both expressed. KEY: both alleles are expressed with no blending. KEY: both alleles are expressed with no blending. Example: Example: In horses, red hair + white hair = roan (red and white hairs). In horses, red hair + white hair = roan (red and white hairs). Two alleles for a gene are both expressed. Two alleles for a gene are both expressed. KEY: both alleles are expressed with no blending. KEY: both alleles are expressed with no blending. Example: Example: In horses, red hair + white hair = roan (red and white hairs). In horses, red hair + white hair = roan (red and white hairs).

Multiple Alleles One of several alleles can be at a given locus One of several alleles can be at a given locus Example: human blood types (A, B, AB, O) Example: human blood types (A, B, AB, O) One of several alleles can be at a given locus One of several alleles can be at a given locus Example: human blood types (A, B, AB, O) Example: human blood types (A, B, AB, O)

Human Blood Types Dominant Alleles I A and I B Recessive Allele i Dominant Alleles I A and I B Recessive Allele i

I A I A type A blood I A i type A I B I B type B I B i type B I A I B type AB ii type O I A I A type A blood I A i type A I B I B type B I B i type B I A I B type AB ii type O

Suppose a woman who has type AB blood marries a man who is heterozygous for blood type A. What blood types might their children have?

type AB x heterozygous type A IAIA IAIA IBIB IBIB IAIA IAIA i i I A I A I B I A i I B i

Dihybrid Crosses Genetic crosses dealing with TWO characteristics at the same time Genetic crosses dealing with TWO characteristics at the same time Example: green/yellow peas AND tall/short pea plants Example: green/yellow peas AND tall/short pea plants Genetic crosses dealing with TWO characteristics at the same time Genetic crosses dealing with TWO characteristics at the same time Example: green/yellow peas AND tall/short pea plants Example: green/yellow peas AND tall/short pea plants

Mendel’s Concept of Independent Assortment The segregation of one set of alleles during gamete formation is not affected by another set. The segregation of one set of alleles during gamete formation is not affected by another set.

Multiple Gene Interaction Sometimes two or more genes working together result in a single trait. Sometimes two or more genes working together result in a single trait. Examples: many human traits such as hair color and skin color Examples: many human traits such as hair color and skin color Sometimes two or more genes working together result in a single trait. Sometimes two or more genes working together result in a single trait. Examples: many human traits such as hair color and skin color Examples: many human traits such as hair color and skin color

Sex-Linked Traits

Two Types of Chromosomes Autosomes Autosomes non-sex-determining chromosomes non-sex-determining chromosomes humans = 22 pairs humans = 22 pairs Sex chromosomes Sex chromosomes XX = female XX = female XY = male XY = male Autosomes Autosomes non-sex-determining chromosomes non-sex-determining chromosomes humans = 22 pairs humans = 22 pairs Sex chromosomes Sex chromosomes XX = female XX = female XY = male XY = male

Female = XX Male = XY X X X X X X Y Y XX XY

Sex-Linked Traits Some genes are carried on the sex chromosomes. Some genes are carried on the sex chromosomes. The X and Y chromosomes are not homologous. The X and Y chromosomes are not homologous. Some genes are carried on the sex chromosomes. Some genes are carried on the sex chromosomes. The X and Y chromosomes are not homologous. The X and Y chromosomes are not homologous.

Sex-Linked Traits Males inherit more sex-linked disorders because they only have one gene for the trait. Males inherit more sex-linked disorders because they only have one gene for the trait. If there is a defective gene on X, there wouldn’t be a normal gene on Y to counteract it. If there is a defective gene on X, there wouldn’t be a normal gene on Y to counteract it. Males inherit more sex-linked disorders because they only have one gene for the trait. Males inherit more sex-linked disorders because they only have one gene for the trait. If there is a defective gene on X, there wouldn’t be a normal gene on Y to counteract it. If there is a defective gene on X, there wouldn’t be a normal gene on Y to counteract it.

Sex-Linked Traits Indicated with a superscript above the X and Y chromosomes Indicated with a superscript above the X and Y chromosomes Example: Example: X H X h X H X h X H Y X H Y Indicated with a superscript above the X and Y chromosomes Indicated with a superscript above the X and Y chromosomes Example: Example: X H X h X H X h X H Y X H Y

Human Examples Red-green colorblindness Red-green colorblindness Hemophilia Hemophilia Lack a blood chemical that allows for blood clotting Lack a blood chemical that allows for blood clotting Red-green colorblindness Red-green colorblindness Hemophilia Hemophilia Lack a blood chemical that allows for blood clotting Lack a blood chemical that allows for blood clotting

X H X H normal female X H X h carrier female A heterozygous female that does not have the disease, but she does carry the gene for the trait X h X h hemophiliac female X H Y normal male X h Y hemophiliac male X H X H normal female X H X h carrier female A heterozygous female that does not have the disease, but she does carry the gene for the trait X h X h hemophiliac female X H Y normal male X h Y hemophiliac male

carrier female x normal male XHXH XHXH XhXh XhXh XHXH XHXH Y Y X H X H X h XHYXHY XHYXHY XhYXhY XhYXhY