Presentation is loading. Please wait.

Presentation is loading. Please wait.

Genetics Chapter 12.

Similar presentations


Presentation on theme: "Genetics Chapter 12."— Presentation transcript:

1 Genetics Chapter 12

2 12-1: Origins of Hereditary Science

3 Mendel’s Experiments Genetics – The study of how characteristics are transmitted from parents to offspring Heredity – The passing on of genetic characteristics from one generation to another

4 Mendel’s Experiments Gregor Mendel (an Austrian monk) used cross-pollination techniques in which pollen is transferred between flowers of two different plants.

5 Mendel’s Experiments Reasons Mendel used pea plants
Require little care Produce many offspring Mature quickly (8-10 weeks)

6 Mendel’s Experiments P (parental) generation – Organisms that are true-bred for specific traits F1 generation – Offspring of the P generation F2 generation – Offspring of the F1 generation F = Filial (pertainting to a son or daughter)

7 Mendel’s Experiments Self-pollination – A plant with both male and female reproductive organs that fertilizes itself Cross-pollination – Pollen from one plant is carried to the flower of another plant

8 Mendel’s Experiments Three Steps of Mendel’s Experiments

9 Mendel’s Experiments Gene – A section of DNA that carries the information on how to make one protein

10 Mendel’s Experiments Allele – An alternative form of a gene
One allele for each trait is passed from each parent to the offspring.

11 Mendel’s Experiments Dominant trait – An allele that is fully expressed whenever the allele is present in an individual The trait that masks the other Recessive trait – An allele that is expressed only when there is no dominant allele present in an individual The trait that is masked

12 12-2: Genetic Crosses

13 Monohybrid Cross Monohybrid cross – A cross in which one characteristic is tracked Punnett square – used to predict the outcome of genetic crosses

14 Monohybrid Cross Genotype – the genetic makeup of an organism (use letters) Phenotype – the appearance of an organism (physical appearance)

15 Monohybrid Cross Homozygous – having identical alleles
Heterozygous – having different alleles

16 Monohybrid Cross Trait – Plant height Phenotype Genotype T – tall
t – short Genotype TT – homozygous dominant (pure bred) Tt – heterozygous (hybrid) tt – homozygous recessive (pure bred)

17 Monohybrid Cross Probability – the likelihood that a specific event will occur Probability = number of one kind of possible outcome total number of all possible outcomes A probability may be expressed as a decimal, a percentage, or a fraction

18 Mendel’s Characteristics

19 Monohybrid Cross Ratios and percentages TT x tt = 100% heterozygous
TT x TT = 100% homozygous dominant tt x tt = 100% homozygous recessive Tt x tt 50% heterozygous 50% homozygous recessive

20 Monohybrid Cross Ratios and percentages
Tt x Tt = Genotypic ratio – 1:2:1 ratio 25% homozygous dominant 50% heterozygous 25% homozygous recessive Tt x Tt = Phenotypic ratio – 3:1 75% tall 25% short

21 Dihybrid Cross Dihybrid cross – A breeding experiment that tracks the inheritance of two traits Example Traits: Seed shape & Seed color Alleles: R – round r – wrinkled Y – yellow y – green

22 Dihybrid Cross RrYy x RrYy
Use the FOIL method for each parent to set-up the Punnett square RrYy x RrYy RY Ry rY ry RY Ry rY ry

23 Dihybrid Cross RY Ry rY ry RY Ry rY ry

24 Dihybrid Cross RY Ry rY ry Round/Yellow: 9 Round/green: 3
Mendelian Genetics 4/23/2017 Dihybrid Cross RY Ry rY ry Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy 24 24

25 Why eye color changes in people is unknown
The trait for eye color actually has three alleles: AaBbCc This chart is used to illustrate the variety of eye colors

26 Other Monohybrid Crosses
Incomplete dominance – a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele This results in a combined phenotype.

27 Other Monohybrid Crosses
Codominance – Two alleles are expressed (multiple alleles) in heterozygous individuals Two alleles that are both dominant Example: blood types Key A = IA B = IB O = I A and B are dominant over O

28 Other Monohybrid Crosses
Genotypes Phenotypes Type A = IAIA or IAi AA or AO Type B = IBIB or IBi BB or BO Type AB = IAIB AB Type O = ii OO

29 Other Monohybrid Crosses
Sex-Linked traits – Traits (genes) located on sex chromosomes X – Female sex chromosome Y – Male sex chromosome Many sex-linked traits carried on X chromosome

30 Pedigree Pedigree – A diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships


Download ppt "Genetics Chapter 12."

Similar presentations


Ads by Google