Genetics

Genetics

Introduction to genetics

TEK: B.6F

Predict possible outcomes of various genetic combinations such as monohybrid crosses, dihybrid crosses and non-Mendelian inheritance.

EQ: What is genetics and what role does DNA/RNA have in it?

Open Ended

BACKGROUND: What do you already know about genetics?

What macromolecule is responsible for carrying our traits?

Multiple Choice

Genetics is the study of heredity. Heredity is the passing of traits

Genetics is the STUDY of HEREDITY

How traits and characteristics are passed on from parents to offspring!

What is the definition of Genetics?

• Study of genes only

• Study of heredity and how traits are passed from parents to offspring.

• Study that involves only humans

Multiple Choice

Heredity is the transfer of gene from parents to offspring.

Chromosomes composed of genes are carried by the sperm and the egg.

When sperm and egg meet=fertilization

Which of the statements are true?

• The only way that we can get genetic information is through fertilization

• Fertilization is just one way that humans obtain their genetic information.

Multiple Choice

A gene is a segment of chromosome that determines/ controls traits.

Traits are specific characteristics for example hair color and eye color are traits

Hereditary factors that make up genes are called alleles. An individual carries two alleles for each trait, one from the mother and one from the father. EX. Ee, EE, ee alleles for eye color

Which of the following is false?

• Genes are segments of DNA that code for our traits. Our heredity factors are represented by alleles that are in pairs.

• Genes are segments of DNA that code for our traits. Our heredity factors are represented by alleles that are in triplets.

Multiple Choice

One chromosome from each parent is inherited. The paired chromosomes are called homologous chromosomes.

TRUE/FALSE

Homologous Chromosomes have the same genetic information for traits. One chromosome is inherited from your mother and the other chromosome is from your father.

• True

• False

Crossing over is the process of which homologous chromosomes exchange segments happens in meiosis.

Crossing over increases genetic variation amoung organisms.

Multiple Choice

TRUE/FALSE

Crossing over events DECREASE genetic variation.

• True

• False

Dominant and recessive alles

• Dominant allele=capital letter Dominant allele shows up (overrides recessive allele

• Recessive allele= lower case letter For example: widow’s peak hairline is dominant over non widow’s peak hairline.

Phenotype and Genotype

• Phenotype of an organism is physical appearance, visible characteristics

• Genotype of organism is actual genetic makeup of the organism, alleles organism possesses. 

Multiple Choice

Which pair of alleles show are both DOMINANT ALLELES?

• aa

• AA

• Aa

Multiple Choice

Which image below represents Phenotype?

Multiple Choice

Which image below represents genotype?

Multiple Choice

Which set of alleles are both recessive alleles?

• AA

• aa

• Homozygous for a trait = 2 of the same alleles

• Homozygous dominant= TT 

• Homozygous recessive= tt

• Heterozygous= 2 different alleles

• Heterozygous Tt 

Multiple Select

Which of the following show homozygous alleles?

Multiple Choice

Which of the following represent heterozygous alleles?

Hybrid and Purebred

• Crosses between parents with different traits are hybrids Hybrids are Heterozygous Ex. Tt    You are a hybrid

  
  

  Purebreds= cross between parents with same traits   Homozygous alleles make a purebred Ex. TT, tt

• We are hybrids in these terms

Multiple Choice

Which of the following allele pair represents hybrid?

• Aa

• aa

Mendel's Two Laws

• Law of segregation- every individual has 2 alleles of each gene. Each gamete receives one of these alleles.

• Law of independent assortment- genes for different traits can segregate (separation of alleles) independently during formation of gametes. This means the emergence of one trait will not affect the emergence of another trait. 

Gregor Mendel: Scientist of Genetics

• Little was understood about heredity until the 19th century when an Australian monk/scientist named Gregor Mendel experiments with pea plants led to some of the founding principles of genetics 

  
  

• Mendel used true- breeding pea plants in his experiments.

• True breeding means plant can self pollinate and the plants produced would be identical to parent plant.

Traits of Pea Pod plants that Mendel studied

What do you notice about the pea pod plant?

Open Ended

What are some of the traits Mendel Studied?

Generations of offspring

• 1st generation or parent is always P1 generation

• F1 generation offspring of parents

• F2 generation offspring of F1

Multiple Choice

If you grandparents would represent the 1st generation then you would represent what generation?

• F1 Generation

• F2 Generation

Multiple Choice

If your grandparents represented the 1st generation then your parents would represent what generation?

• F1 Generation

• F2 Generation

Non-Mendelian Genetics

All of the exceptions to the rules

1. Incomplete Dominance

2. Codominance

Multiple Alleles

Polygenic Traits

Incomplete Dominance

• Neither allele is dominant resulting in a blending of traits. 

• Red flower and white flower=pink flower

• Key word: Blending

Codominance

• Both traits expressed simultaneously. 2 traits are equally dominant

• Black and white speckled chicken

• Both Traits are seen!

Multiple Alleles

• more than 2 alleles controlling a particular gene.  Blood type is an example.

• Alleles for A and B are codominant (IAIB) and the allele for O is recessive (ii).

• 4 phenotypes produced by 3 different alleles

• Blood type is an example.

Polygenic Traits

• traits controlled by two or more genes

• Examples: eyes, skin, and hair

Probability

likelihood of a particular event occurring

Multiple Choice

Given the following Punnett square, what is the probability the offspring will be yellow?

• 0%

• 25%

• 50%

• 75%

• 100%

Multiple Choice

Given the following Punnett square, what is the probability the offspring will be green?

• 0%

• 25%

• 50%

• 75%

• 100%

Multiple Choice

Given the following Punnett square, what is the probability the offspring will be yellow?

• 0%

• 25%

• 50%

• 75%

• 100%