GENETICS QUICK INTRODUCTION

QUICK COURSE OF GENETICS

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HEREDITY

It’s why we look like our parents! More specifically, it is the transmission of traits from one generation to the next. These traits can be physical, such as eye colour, blood type or a disease, or behavioural.

Naturalism: All beings and events in the universe (whatever their inherent character may be) are natural.

THE RISE OF NATURALISM

Theism: Belief in the existence of a god or gods, specifically of a creator who intervenes in the universe.

The development of experimental methods

1884

1670

1600

1595

Advances in microscopy

GREGOR MENDEL AND HEREDITY LAWS

GREGOR MENDEL, 1822-1884

Pea Plant(Pisum sativum L.)

Mendel crossed pure-breeding lines of plants

Principle of Dominance

Principle of Dominance

Law of Segregation

Law of Independent Assortment

HEREDITY LAW'S

Law of Segregation: When gametes form, alleles are separated so that each gamete carries only one allele for each gene.Law of Independent Assortment: The segregation of alleles for one gene occurs independently to that of any other gene*.Principle of Dominance: Recessive alleles will be masked by dominant alleles†

Segregation of Flower Color

In pea plants, flower color is determined by a single gene with two alleles: Y (yellow) and y (white). Yellow flower color is dominant over white flower color. a) Cross a true-breeding yellow-flowered pea plant with a true-breeding white-flowered pea plant. Use a Punnett square to predict the genotype and phenotype of the F1 offspring. b) Cross two F1 plants from the previous cross. Use a Punnett square to predict the genotype and phenotype ratios of the F2 offspring.

Independent Assortment of Seed Shape and Seed Color

In pea plants, seed shape is determined by a single gene with two alleles: R (round) and r (wrinkled). Round seed shape is dominant over wrinkled seed shape. Seed color is determined by a single gene with two alleles: Y (yellow) and y (green). Yellow seed color is dominant over green seed color. a) Cross a true-breeding yellow-seeded, round-seeded pea plant with a true-breeding green-seeded, wrinkled-seeded pea plant. Use a Punnett square to predict the genotype and phenotype of the F1 offspring. b) Cross two F1 plants from the previous cross. Use a Punnett square to predict the genotype and phenotype ratios of the F2 offspring.

Dominance and Recessiveness in Pea Pod Shape

In pea plants, pod shape is determined by a single gene with two alleles: L (long) and l (short). Long pod shape is dominant over short pod shape. a) Cross a homozygous dominant pea plant with a homozygous recessive pea plant. Use a Punnett square to predict the genotype and phenotype of the F1 offspring. b) Cross two F1 plants from the previous cross. Use a Punnett square to predict the genotype and phenotype ratios of the F2 offspring.

In snapdragons, stem height is determined by a single gene with two alleles: T (tall) and t (short). Tall stem height is dominant over short stem height. Flower color is determined by a single gene with two alleles: R (red) and r (white). Red flower color is dominant over white flower color. a) Cross a true-breeding red-flowered, tall-stemmed snapdragon plant with a true-breeding white-flowered, short-stemmed snapdragon plant. Use a Punnett square to predict the genotype and phenotype of the F1 offspring. b) Cross two F1 plants from the previous cross. Use a Punnett square to predict the genotype and phenotype ratios of the F2 offspring.

Independent Assortment of Stem Height and Flower Color in Snapdragons

DNA REPLICATION

• X (Turner syndrome)
• X-XY Klinefelter syndrome
• Trysome 18 - Edwards Syndrome

DEFINITION

Replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules.

Helicase

Primer

Helicase

Primase

DNA POLIMERASE 5' --> 3'

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Chatterjee and Walker, 2017

DNA TRANSCRIPTION

Transcription

Transcription is the first step of gene expression. During this process, the DNA sequence of a gene is copied into RNA.

RNA POLYMERASE

RNA polymerases are enzymes that transcribe DNA into RNA. Using a DNA template, RNA polymerase builds a new RNA molecule through base pairing.

RNA POLYMERASE

RNA polymerases are enzymes that transcribe DNA into RNA. Using a DNA template, RNA polymerase builds a new RNA molecule through base pairing.

Elongation

During elongation, RNA polymerase "walks" along one strand of DNA, known as the template strand, in the 3' to 5' direction. For each nucleotide in the template, RNA polymerase adds a matching (complementary) RNA nucleotide to the 3' end of the RNA strand.

TerminationRho-dependent

When it catches up with the polymerase at the transcription bubble, Rho pulls the RNA transcript and the template DNA strand apart, releasing the RNA molecule and ending transcription.

TerminationRho-independent

• As the RNA polymerase approaches the end of the gene being transcribed, it hits a region rich in C and G nucleotides.
• In a terminator, the hairpin is followed by a stretch of U nucleotides in the RNA, which match up with A nucleotides in the template DNA. The complementary U-A region of the RNA transcript forms only a weak interaction with the template DNA.

RNA TRANSLATION

sOURCES OF GENETIC VARIABILITY