Introduction to Genetics Part 2 Dihybrid Crosses Karyotypes Chromosomes Mutations

Genetic Diversity Genetic Diversity means that all organisms within the same species are not exactly alike due to their genetic material (unless they are identical twins) Genetic diversity is usually good: Example:If everything was exactly the same, then one disease that they were not immune to could wipe the species out!!

Genetic Diversity Genetic Diversity is caused by two processes: Crossing over which occurs in Prophase I of Meiosis Independent Assortment of the chromosomes which occurs in Anaphase II when the sister chromatids separate randomly into a gamete

Crossing Over

Independent Assortment

Dihybrid Punnett Square A way to show all the combinations of TWO traits that sort independently of each other Example:

FOIL Method of determining Parental Gametes Genotype If parental genotype is AaBb Then gamete combos would be: First allele (letter) of each trait (AB) Outside alleles : (Ab) Inside alleles: (aB) Last alleles: (ab) These are the choices that go into your Punnett Square – see previous slide

You Try If your parent genotype was AABb Determine your 4 gamete combos: (some may be the same as each other) Show a dihybrid Punnett square if both parents were the above genotype.

In humans, wide nostrils are dominant to narrow nostrils and a convex nosebridge is dominant to a straight nose bridge. Show the genetic possibilities: a man who is heterozygous for wide nostrils and a convex nosebridge marries and THEN has children with a woman who is heterozygous for both traits Determine parent genotypes Determine parental gametes. Set up Punnett Square (16 squares) Fill in offspring (F1) genotypes Determine phenotype ratio - Use the following format D = dominant and R = recessive DD:DR:RD:RR Wide nostriled with a convex nosebridge ______ Wide nostriled with a straight nosebridge ______ Narrow nostriled with convex nosebridge ______ Narrow nostriled with straight nosebridge______

Polygenic Traits Some traits are controlled by multiple genes working together Human eye & hair color are examples of these These are a little harder to predict since there are so many combinations

Eye Color

Assignment Complete the Dihybrid Punnett Square Worksheet It will be due in 2 days

Evaluating Dihybrid Crosses Analyze the following TAKS questions

Chromosomal Mutations & Karyotypes

Terminology Gamete: Sex cells (egg & sperm) Somatic Cell: All other body cells Sex Chromosomes: X and Y chromosomes – designated 23 rd pair XX = female Xy = male Autosomes: The other 22 pairs of chromosomes

Important Info A human gamete contains the haploid number or 23 chromosomes A human somatic cell contains the diploid number or 46 chromosomes 23 pairs = 1 set of 23 from mom and 1 set of 23 from dad

Chromosome Mutations There is a change in the number or structure of the chromosomes Make sure you can recognize examples & descriptions of each type

These are the types of Chromosome Mutations we will be learning Deletion Duplication Inversion Translocation Nondisjunction

Deletion Mutation

Duplication Mutation

Inversion & Translocation Mutations

Nondisjunction Mutations

Karyotype – arrangement of all chromosomes

Nondisjunction Karyotype

Analyze this Karyotype

Karyotype Activity We will be beginning a karyotype activity today and completing it in class tomorrow. Please make sure you get all your chromosomes cut out today. If you do not get them all glued onto your paper today – please get a baggie to store them in till tomorrow. We will be finishing the activity in class tomorrow – the questions will be due by the following day

Pedigree Charts write these notes & examples down on NB paper to study for your test How to track inheritance through a family tree

Basic Info Pedigrees are family trees that explain your genetic history. Pedigrees are used to find out the probability of a child having a disorder in a particular family. To begin to interpret a pedigree, determine if the disease or condition is dominant or recessive. (There are other types but we will not be interpreting those)

Constructing a Pedigree Male Female

Connecting Pedigree Symbols Married Couple Children Examples of connected symbols:

Example What does a pedigree chart look like?

Symbols in a Pedigree Chart Carriers of a recessive trait are shown by a symbol that has only one side colored in.

Interpreting a Pedigree Chart Determine whether the disorder is dominant or recessive. If the disorder is dominant, one of the parents must have the disorder. If the disorder is recessive, neither parent has to have the disorder because they can be a heterozygous carrier.

Example of Pedigree Charts Dominant or Recessive? Explain using the genotypes

Answer Dominant – at least one parent of each affected individual has the disorder

Example of Pedigree Charts Dominant or Recessive? Explain using the genotypes

Answer Recessive – an affected individual can have 2 parents without the disorder who are heterozygous (carriers)

Assignment Work with a partner to complete the assignment on pages in your text. You will need to write down your plan but will not be presenting it to the class. You and your partner will take it to your teacher to check it when you finish. Then continue working on your review sheet & studying for your test.