Mendel and Heredity Mendel and Heredity Terms Gregor

Mendel and Heredity

Mendel and Heredity Terms • Gregor Mendel- “Father of Genetics” • Traits- characteristics that are inherited – Ex. Eye color, hair color • Genetics- study of biological inheritance patterns • Purebred- offspring inherit all of parents characteristics, genetically uniform

Mendel and Heredity Terms • Cross- mating of two organisms • Gene- piece of DNA that provides a set of instruction to a cell • Allele- any alternative form of a gene that may occur

Mendel and Heredity Terms • Homozygous- two of the same alleles • Heterozygous- two different alleles

Mendel and Heredity Terms • Genotype- genetic makeup of a specific set of genes • Phenotype- physical characteristics or appearance of an organism • Dominant- allele is expressed when two different alleles are present • Recessive- allele is expressed only when two copies are present

Genetics • In the 1800’s, Gregor Mendel laid the groundwork for modern genetics • He crossed many pea plants and observed traits of offspring • Discovered that – Organisms inherit two copies of each gene, one from each parent

Genetics • Peas either: – Round (dominant) – Wrinkled (recessive) • Genotypes – RR (homozygous dominant) – Rr (heterozygous) – rr (homozygous recessive) Phenotypes -round -wrinkled

Genetics • Another example: • Brown (dominant) vs. black (recessive) • Genotypes? Phenotypes?

Genetics • Mendel’s discoveries led to the Punnett square • Developed by R. C. Punnett • Used to predict genotypes of offspring • Example: – Straight (dom. ) vs. curly (rec. ) – Dad-heterozygous – Mom-homozygous recessive

Dihybrid Punnett Square • Predicting more than one trait • EX. Cross a tall pea plant with green leaves with a short pea plant with yellow leaves. 1. 2. 3. 4. Determine parent genotypes. Find combinations of alleles. Fill out Punnett square. Determine phenotypes of offspring.

Dihybrid Punnett Square • EX. Cross a tall (homozygous) pea plant with green (heterozygous) leaves with a short pea plant with yellow leaves. (Tall is dominant to short, green is dominant to yellow)

Dihybrid Practice • Cross the parents Ss. Yy x Ss. Yy SY Sy s. Y sy SY SSYY Sy SSYy Ss. YY Ss. Yy Ssyy Ss. YY Ss. Yy ss. YY ss. Yy sy Ss. Yy Ssyy ss. Yy ssyy s. Y Smooth/Yellow __9____ Smooth/Green ___3___ Rough/Yellow ____3__ Rough/Green _____1_

Bellringer: Complete both questions in your notebook • 1. In one particular species of cats, long hair is dominant to short hair. If a heterozygous male is crossed with a homozygous recessive female, what is the probability that one of the offspring has long hair? • 2. A homozygous dominant flower is crossed with a homozygous recessive flower. Purple flowers are dominant to red flowers. What are the genotypes and phenotypes of the offspring?

Sex-linked Genes • Sex-linked genes- genes located on the sex chromosomes – Female (XX), Male (XY) X Y X XX XY X

Incomplete Dominance • Alleles that show incomplete dominance show both the dominant and recessive traits • Neither allele is completely dominant or recessive • Ex. If a homozygous red flower and homozygous white flower cross, the offspring have pink flowers

Codominance • Both the dominant and recessive alleles are expressed • Ex. Red and white flower are crossed, the offspring will be red and white

Exit Slip 1. Sex linked genes are located _______. 2. A dog that shows the phenotypes of both his mother and father would be an example of (incomplete or codominance). 3. A blue flower crosses with a yellow flower to produce a green flower. This is an example of (incomplete or codominance).

Pedigree • Pedigree- chart that can help trace phenotypes and genotypes in a family – Helps to determine if people carry the recessive allele

Pedigree

Pedigree • Reading a pedigree

Example ○ □ □ ○ How many boy children? How many girl children? Is the oldest child a boy or girl? □

Griffith Experiment

DNA Structure • DNA is a polymer made of monomers called nucleotides • Each nucleotide is made of: – A phosphate group – Deoxyribose (sugar) – Nitrogen containing base

Types of Nucleotides • C – Cytosine Pyrimidines • T – Thymine • A – Adenine Purines • G – Guanine

Base-Pairing Rules • Nucleotides always pair in the same way – Thymine (T) always pairs with Adenine (A) – Cytosine (C) always pairs with Guanine (G) – Ex. TTACGTAG AATGCATC

DNA Structure • DNA is in the shape of a double helix • Each nucleotide is paired

Exit Slip 1. Thymine is an example of a _______. • nucleotide 2. The shape of DNA is known as a ______. • Double helix 3. Write the DNA base pair: TCGGAATCCACGTG ________ – AGCCTTAGGTGCAC

DNA Replication • Replication is a process by which DNA is copied • Occurs during the S stage of the cell cycle