Patterns of inheritance

Slides:



Advertisements
Similar presentations
Chapter 11 Mendel & The Gene Idea.
Advertisements

Genetics SC Biology Standard B The students will be able to predict inherited traits by using the principles of Mendelian Genetics, summarize.
Ch 11- Introduction to Genetics
Unit 8 Introduction to Genetics
Patterns of inheritance
Unit 6 Genetics: the science of heredity
PATTERNS OF INHERITANCE
Genetics The Study of Heredity.
CHAPTER 9 Patterns of Inheritance
Mendel’s Laws of Heredity
Patterns of Inheritance
Mendel & Genetics Review Powerpoint
Mendel performed cross-pollination in pea plants.
You have body cells and gametes.
Heredity Unit – Theory of inheritance B-4.7: Summarize the chromosome theory of inheritance and relate that theory to Gregor Mendel’s principles of genetics.
Patterns of Inheritance
Genetics Study Guide Key to Success on the Test. 1. What scientist experimented with pea plants to establish modern genetics? Gregor Mendel.
PATTERNS OF INHERITANCE CAPTER 10. Pre-Mendel’s Theories  Blending Hypothesis: when parents with different traits have offspring, this will always show.
The Experiments of Gregor Mendel Genetics – the study of heredity Mendel – studied ordinary pea plants The Role of Fertilization Pea plants – self-pollinating.
Population Dynamics Humans, Sickle-cell Disease, and Malaria How does a population of humans become resistant to malaria?
Introduction to Genetics Genetics- scientific study of heredity Gregor Mendel- father of genetics, laid the foundation of the science of genetics – Used.
Fundamentals of Genetics Chapter 9 Table of Contents Section 1 Mendel’s Legacy Section 2 Genetic Crosses.
Principles of Mendelian Genetics B-4.6. Principles of Mendelian Genetics Genetics is the study of patterns of inheritance and variations in organisms.
Genetics Review 23 How many pairs of chromosomes do humans have?
Mendel & Genetics Review Powerpoint Gregor Mendel, the father of genetics.
Chapter 9. Vocabulary  Heredity: the transmission of traits from one generation to the next  Genetics: the scientific study of heredity  Character:
Chapter 10 HOW INHERITED TRAITS ARE TRANSMITTED. Genetics is the science of heredity.
Gregor Mendel. Trait: – A specific characteristic that varies from one individual to another.
Genetics Mendelian Genetics Genetic Engineering. Gregor Mendel Used pea plants to experiment on genetic traits Pea plants can self-pollinate, producing.
7.1 Chromosomes and Phenotype
Two copies of each autosomal gene affect phenotype.
7.1 Chromosome and Phenotype
The Basic Principles of Heredity
Difference between a monohybrid cross and a dihybrid cross
Chapter 8 Heredity.
Genotype and Phenotype
KEY CONCEPT Genes can be mapped to specific locations on chromosomes.
Patterns of Inheritance
Chromosomal Mutations/Abnormalities
Chapter 6.
Chapter 6, sections Mendelian Genetics.
Genetics A. The Vocabulary of Genetics
Unit 7 Genetics.
Mendelian Genetics Unit 3 Notes.
Two copies of each autosomal gene affect phenotype.
Mendelian VS. Non-Mendelian Genetics
Bio.B.2- Genetics CHAPTER 11.
Mendel’s Genetics Chapter 7.
Population Dynamics Humans, Sickle-cell Disease, and Malaria
Unit 6 GB JAG Review.
Chapter 11.
Chapter 8 Mendel, Peas, and Heredity
Two copies of each autosomal gene affect phenotype.
Chapter 11 Notes: Mendelian Genetics
Meiosis & Mendel Chapter 6
Introduction to Mendelian Genetics
Mendelian Genetics chapter 10.1
Biology.
Using Punnett Squares A Punnett square is a model that predicts the likely outcomes of a genetic cross. A Punnett square shows all of the genotypes that.
Two copies of each autosomal gene affect phenotype.
Unit 5: Heredity Review Lessons 1, 3, 4 & 5.
Genetics.
Two copies of each autosomal gene affect phenotype.
Mendel and the Gene Idea
Two copies of each autosomal gene affect phenotype.
Introduction to Genetics
7.1 Chromosomes and Phenotype
Chapter 12 Mendel’s Genetics
Heredity and Genetic Analysis
Genetics Chapters 6 and 7.
Presentation transcript:

Patterns of inheritance Chapter 10 Patterns of inheritance

10.1 Chromosomes are packets of genetic information Terms to review Gene- portion of a dna that codes for a protein or RNA Alleles- versions of a gene Chromosomes- molecule of DNA and associated proteins Diploid cell- complete set of chromosomes Autosomes- chromosomes that do not determine gender Sex chromosomes- determine gender (XX or XY) Homologous pair- chromosomes with matching genes Fertilization- two gametes fuse creating a zygote

10.2 Mendel’s experiments uncovered basic laws of inheritance. Mendel used pea plants to study inheritance. He found that dominant alleles mask recessive alleles. The only way a recessive trait shows up is if two recessive alleles are inherited. For each gene, a cells two alleles may be identical or different.

A genotype is the combination of alleles inherited. Homozygous means two identical alleles were inherited(either dominant or recessive) Heterozygous means one of each type was inherited. Phenotype is the organisms appearance or observable characteristics. Wild-type allele, phenotype, or genotype is the most common form or expression of a gene in a population. Mutant allele, phenotype, or genotype is a variant that arises when a gene undergoes a mutation.

Every generation has a name: P generation- parental F1 is the first filial generation- offspring of P generation F2 is the offspring of the F1 generation.

Chapter 10 Section 3

A. Monohybrid crosses track the inheritance of one gene Mendel discovered that when two organisms that are heterozygous for a trait are crossed, they exhibit both phenotypes in a 3:1 ratio, dominant to recessive. A monohybrid cross looks at one trait only. A punnett square is a diagram used to show alleles combinations that offspring may inherit.

A test cross is used to show if the genotype of a dominant phenotype is heterozygous or homozygous recessive. The organism with the unknown phenotype is crossed with a homozygous recessive mate.

B. Meiosis explains Mendel’s Law of segregation Not only did Mendel discover alleles, he also deduced the Law of Segregation. This law states that the two alleles of each gene are packaged into separate gametes. They segregate or move apart from each other during gamete formation. This principle applies to all diploid species. Punnett squares show probabilities.

10.4 Genes on Different chromosomes are inherited independently A. dihybrid crosses track the inheritance of two genes at once. Mendel wondered if traits influenced the inheritance of other traits. He set up dihybrid crosses to test this. A dihybrid cross is a mating between two individuals that are heterozygous for two genes. The four genotypes possible occur in a ratio of 9:3:3:1

B. Meiosis explains Mendel’s law of independent assortment Law of independent assortment states that during gamete formation, the segregation of the alleles for one gene does not influence the alleles for another gene(if the genes are on separate chromosomes) The alleles are randomly packaged into gametes with respect to each other.

Punnett squares for more than two traits are very large. An easier way to predict genotypes and phenotypes is to use the product rule. This states that the chance that two independent events will both occur equals the product of the individual chances that each event will occur.

10.5 Genes on the same chromosome may be inherited together A. Genes on the same chromosome are linked. Linked genes are genes that are carried on the same chromosome, so they are inherited together. They do not assort independently First noticed by Bateson and Punnett when they observed different ratios than predicted by Mendel’s laws.

Thomas Hunt Morgan found the same type of patterns in fruit flies Thomas Hunt Morgan found the same type of patterns in fruit flies. He found four linkage groups(collections of genes inherited together). Each linkage group was simply a set of genes transmitted together on the same chromosome. Sometimes, the scientists would see gene combinations that were not present in either parent. This is because of crossing over that occurs during meiosis. Offspring either inherit a parental chromatid or a recombinant chromatid.

B. Studies of linked genes have yielded chromosome maps Sturtevant found that the closer together two genes are on a chromosome, the less likely they are to be separated by crossing over. The further apart, the more likely to be separated. This led to create linkage maps which are diagrams of gene order and spacing on chromosomes.

Phenotypes were once used to make linkage maps, but now gene markers are used. These are valuable for showing probability of inheriting certain genetic disorders.

10.6 Gene expression can appear to alter Mendelian ratios A. Incomplete dominance and co-dominance Mendel studied complete dominance but sometimes the heterozygous offspring do not have the trait of either parent. Examples- incomplete dominance- heterozygous has a third phenotype that is intermediate. It looks like a blending of traits.

Co-dominance- two different alleles are expressed together in the phenotype. Example- blood types and roan fur color

B. Some patterns are difficult to interpret Pleiotropy- one gene has multiple effects on the phenotype. This happens when one protein is important in different biochemical pathways or affects more than one body part or process. Example- Marfan Syndrome and porphyrin

Ex. Blood clotting, porphyra Protein interactions- Many proteins can interact to contribute to a single phenotype. This complicates the analysis of inheritance patterns. Ex. Blood clotting, porphyra Epistasis- when one genes product affects the expression of another gene. Example- male pattern baldness, and inconsistencies in ABO blood type patterns.

10.7 Sex linked genes have unique inheritance patterns A. X and Y chromosomes determine sex in humans XX is female XY is male The y chromosome plays the biggest part in human sex determination. An embryo that has a working copy of the SRY gene develops into a male because the gene encodes a protein that switches on genes that direct the testes to produce testosterone. Other reactions are also switched on. SRY also turns on a gene encoding a protein that dismantles female structures.

The Y chromosome has fewer than 100 genes so there are very few Y linked disorders- most involve defects in sperm production.

B. X-linked recessive disorders affect more males than females The X chromosome carries more than 1000 protein coding genes. Therefore most sex linked traits are X-linked. More males show X-linked traits because the Y chromosome does not have a corresponding gene to “mask” the gene from the X chromosome. Most X-linked traits are caused by recessive alleles. Females can only show the trait if they have two recessive alleles. The male shows the trait whether it is recessive or dominant.

C. X inactivation prevents “double dosing” of proteins Since female cells have two X chromosomes, they have a double dose of proteins that are coded for on the X chromosome. One X chromosome is inactivated at random in each cell. This is why females who are heterozygous for an X linked disorder will have less severe symptoms than a male.

10.8 Pedigrees show modes of inheritance Pedigrees are diagrams used to show the passing down of traits through generations for autosomal dominant and autosomal recessive traits. Heterozygous individuals are “carriers” for the trait. X-linked recessive conditions show unique patterns of inheritance. Pedigrees can be difficult to construct for many reasons.

10.9 most traits are influenced by the environment and multiple genes A. The environment can alter phenotypes- External environment can profoundly affect gene expression Fetal alcohol syndrome, fur color pattern in Siamese cats, depression, type II diabetes.

B. Polygenic traits can alter the phenotype Polygenic- phenotype reflects the activities of more than one gene. Ex. Eye color, skin color Sometimes environment can also influence a polygenic trait. Ex. Height, body weight, skin color, intelligence.