Introduction to Genetics

Allele Dominant Recessive Genotype Phenotype Homozygous OUTCOME QUESTION(S): S1-1-12: How are the features of the parents inherited to create unique offspring? Vocabulary & Concepts  Allele Dominant Recessive Genotype Phenotype Homozygous Heterozygous Punnett Square

Single Trait Inheritance Recall: A GENE is a discrete unit of hereditary information located on a chromosome which codes for a particular trait.   A TRAIT is an observable and distinguishing characteristic of an individual. Ex. Eye and hair color. GENETICS is the branch of science that studies heredity and variation in organisms, specifically how traits are passed from generation to generation. Gregor Mendel & Genetics

Remember: one from “mom,” one from “dad” Allele – alternate forms of a gene. Alleles occupy the same location on homologous chromosomes. eye gene – brown Remember: one from “mom,” one from “dad” eye gene – blue Two different alleles for a gene trait

x x y x Homologous chromosomes have alleles (different versions) of all the same genes

There are 2 types of genes: Recessive alleles & Dominant alleles Recessive allele: gene version that is masked or not expressed. Dominant allele: gene version that determines how the person will look. Recessive alleles only show in offspring when there are no dominant versions present

Your genotype can only be known by undergoing genetic testing The way a person looks (the traits they show) is called their phenotype – can be observed (seen). Black hair, brown eyes… The genes that code for a trait are called a persons genotype - not directly observable. 2 brown alleles for eyes, 1 black and 1 blonde allele for hair colour… Your genotype can only be known by undergoing genetic testing

RR R r r r Capital letters represent a dominant allele Put another way: Genotype refers to your Genetic makeup. Phenotype is your Physical appearance Capital letters represent a dominant allele Lower case represents a recessive allele Three Genotype possibilities: One Allele from dad (sperm) RR R r r r One Allele from mom (egg)

person has two recessive alleles for eyes. Genotype – bb Phenotype – blue eyes Name – homozygous recessive person has two dominant alleles for eyes. Genotype – BB Phenotype – Brown eyes Name – homozygous dominant person has one dominant and one recessive. Genotype – Bb Phenotype – Brown eyes Name – heterozygous

A person with two different alleles is called Having the same allele on both homologous chromosomes is called homozygous – for that trait. A person with two different alleles is called heterozygous – for that trait. Homozygous for a trait is also called “purebred” Heterozygous is called “hybrid”

Observing Human Traits Lab With your table partner, work through Questions 1-4 In 15 mins, we will collect our class data to complete the rest of Lab.

You must know the genotypes of both parents to start a square Punnett Squares: Shows the possible combinations of alleles from parents when they are crossed (fertilization). Used to predict the genotype and phenotype of any offspring. You must know the genotypes of both parents to start a square

1. State the genotypes for each parent. Eye Size: Father = Ee (heterozygous big eyes) Mother = ee (homozygous small eyes) ** Choose a letter that makes sense to use** 2. Draw Punnett square and place the parents at the top and the left side of the square. 3. Complete the square by combining the possible genes from each parent in each square.

A father (heterozygous for Brown eyes), wants to have children with a homozygous blue eyed mother. What are the chances of a blue eyed baby? Father = Bb Mother = bb ½ offspring will have blue eyes. 50% chance.

Remember: We’re looking at the heredity of ONE gene on ONE homologous pair from parent to offspring.

**sex-linked genes are expressed more often in males than in females** SEX-LINKED TRAITS- Genes carried on the X & Y are often RECESSIVE and carried on the X chromosome. Because males carry one copy of the gene because they only have 1 X chromosome Females carry two copies of the gene because they have 2 X chromosomes **sex-linked genes are expressed more often in males than in females** Carriers – are individuals that are heterozygous for a recessive trait. They “carry” the recessive gene but that gene is not expressed.

THE DIHYBRID CROSS A dihybrid cross is a cross that involves two separate traits. Sample Problem: In pea plants, tall height is dominant over short, and purple flowers are dominant over white flowers. If two heterozygous plants are crossed, what are the genotypes and phenotypes of the F1 generation? The Punnett Square Solution: Write a “let statement” for the symbols to be used. Let T represent the dominant allele (tall height) and t represent the recessive allele (short). Let P represent the dominant allele (purple flowers) and p represent the recessive allele (white).

1) Write down the description of the parents involved, including their genotypes using the correct symbols. Parents’ phenotypes: Tall with purple × Tall with purple flowers flowers Parents’ genotypes: TtPp × TtPp 2) List all possible gametes that could be produced by each parent. One allele from each pair of alleles is passed on to its offspring. There are 4 possible allele combinations for a parent that is heterozygous for two separate traits. Use the FOIL method to figure out the combinations: F = the first two alleles of each trait TP O = the outer two alleles of each trait Tp I = the inner two alleles of each trait tP L = the last two alleles of each trait tp Possible gametes: TP Tp tP tp

CAN YOU ANSWER THESE QUESTIONS? S1-1-12: How are the features of the parents inherited to create unique offspring? Vocabulary & Concepts  Allele Dominant Recessive Genotype Phenotype Homozygous Heterozygous Punnett Square

Adaptations and Mutations Genetic Success Adaptations and Mutations

Natural Selection Adaptation Mutation Mutagen Cancer Carcinogen OUTCOME QUESTION(S): S1-1-08: What are some ways plants and animals improve their chance to reproduce? S1-1-15: How can lifestyle choices affect your genetics and development? Vocabulary & Concepts  Natural Selection Adaptation Mutation Mutagen Cancer Carcinogen

Natural selection is the gradual process of traits becoming more common in a population because the traits may improve reproductive success of organisms in an environment. (It is a key mechanism of evolution) Luck and timing has something to do with it too…

Think of traits that have evolved to help an organism (including humans) survive its environment and reproduce.

disadvantage : no offspring Anything that gives you an advantage will help you pass that positive trait on to offspring disadvantage : no offspring

“Only The Strong Survive” Adaptation: a naturally selected trait that enhances reproductive success. Can be physical or behavioural How would big tail feathers make him more successful? How would they make him less successful?

Examples of Adaptations Behavioural caring for young mating calls dances fighting Physical colours / camouflage size / shape pheromones multiple offspring Those best able to modify their behavior or those with positive alleles that improve their survival and reproductive success pass on these traits to future offspring

Mutation: A mistake or error resulting in an incorrect DNA sequence with parts lost, changed or mixed. Gene mutation: change in an individual gene or segment Chromosomal mutation: changes in total number present Common Gene Mutations

Natural causes of mutation: Spontaneous copying or separation error Aging Obesity and poor diet Environmental causes of mutation: Exposure to chemicals/toxins called mutagens ~ pollution, pesticides, tobacco, alcohol, food additives… Exposure to ionizing radiation (UV, X-rays) Infection by some viruses Gamete mutation: can be passed on Somatic (body cell) mutation: not passed on

Somatic cells mutate once every 3 billion reproductions Genetic mutations are common but very rarely are they serious mutations: Usually recessive and masked by dominant allele Usually insignificant in the effect on the body Somatic cells mutate once every 3 billion reproductions

Gene and/or Chromosomal Disorders Down Syndrome Tourette Syndrome Turner’s Syndrome Lupus Huntington's Disease Cystic Fibrosis Sickle-cell Anemia Heart Disease Diabetes Cancer Some develop from multiple mutations and environmental causes making them difficult to study and treat

Cancer A mutation that affects cell division: causing spontaneous, uncontrolled division. May involve inherited gene mutations Caused by exposure to environmental mutagens mutagen that triggers cancer - carcinogen A normal cell has “detectors” that tell it when to stop replicating or when it is somewhere it should not be

Quickly dividing mutated cells create a cancerous tumour. Genes controlling cell division are particularly susceptible to mutations. Quickly dividing mutated cells create a cancerous tumour.

CAN YOU ANSWER THESE QUESTIONS? S1-1-08: What are some ways plants and animals improve their chance to reproduce? S1-1-15: How can lifestyle choices affect your genetics and development? Vocabulary & Concepts  Natural Selection Adaptation Mutation Mutagen Cancer Carcinogen