Biology Genetics

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DNA History – Friedrich Miescher studied

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NUCLEI In 1869

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DNA History – Miescher found that the nuclei were

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mildly acidic, and contained phosphorus, carbon, oxygen, and nitrogen.

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DNA History – NUCLEIC ACID

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Miescher coined the term from the fact that these substances were acidic and located in the nuclei of cells.

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DNA History – it was not known whether the DNA or the PROTEIN substances of chromosomes carried hereditary information

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Until the mid-1900s.

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DNA History – In 1928, Frederick GRIFFITH

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conducted bacterial studies and suggested that DNA was the genetic material.

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DNA History – Collaborated In the 1940’s, to study the DNA molecule

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James WATSON collaborated with Francis CRICK at Cambridge University in England.

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DNA History – took the FIRST clear x-ray image of DNA

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in the 1940’s Rosalind FRANKLIN had also been working on the structure of DNA. Through her use of x-ray crystallography, she was able to take the FIRST clear x-ray image of DNA. She discovered that DNA was very long compared to its 3 nm diameter and that repeating units were found at regular intervals.

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DNA History – they utilized this information to model DNA’s structure in 1953

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The work of Rosaline Franklin was brought to the attention of James Watson and Francis Crick and they utilized this information to model DNA’s structure in 1953. In 1962, they received the Nobel Prize for this discovery.

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Function & Structure of DNA

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Deoxyribose Nucleic Acid

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Function & Structure of DNA - DNA controls what makes an organism unique by

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controlling the PROTEIN production that controls the cell.

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Function & Structure of DNA – In eukaryotes DNA is found in

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the NUCLEUS in eukaryotes Function & Structure of DNA – In prokaryotes DNA is found in the CYTOPLASM/STROMA of prokaryotes.

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Function & Structure of DNA – DNA Is an organic compound composed of

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nucleotides (BASE, SUGAR, and PHOSPHATE)

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Function & Structure of DNA – Structure shaped like a twisted ladder

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DOUBLE HELIX

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Function & Structure of DNA – The upright sides of the ladder are formed by alternating molecules of

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DEOXYRIBOSE (a 5-carbon sugar) and PHOSPHATE groups.

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Function & Structure of DNA – The terminal phosphate groups are at different ends from each other, a condition known as

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ANTI-PARALLELL—the backbones are upside-down to each other.

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Function & Structure of DNA – 5’ (five prime) is

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The starting point of the molecule

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Function & Structure of DNA – The ending point is

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3’ (three prime).

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Function & Structure of DNA – The prime ( ˊ ) indication refers to the numbered position of carbon atoms in

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the deoxyribose portion of the molecules.

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Function & Structure of DNA – The rungs of the ladder are pairs of

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nigtrogen bases held together by hydrogen bonds.

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Function & Structure of DNA – There are 4 bases in DNA:

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Adenine (_a__), Thymine (_t__) Cytosine (_c__), Guanine (_g__)

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Nitrogenous Bases -In 1950, Erwin Chargaff first noticed the amounts of A to T and C to G were

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IDENTICAL

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Nitrogenous Bases - Pairing is specific in

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DNA.

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Nitrogenous Bases - Adenine only pairs with

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THYMINE and is held together with 2 hydrogen bonds.

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Nitrogenous Bases - Cytosine only pairs with

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GUANINE and is held together with 3 hydrogen bonds.

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Nitrogenous Bases - write the complimentary DNA to the following A T C G T T C G T C A G

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T A G C A A G C A G T C

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Nitrogenous Bases - How many types of bases are there?

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There are two different types of bases: Purines and Pyramidines

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Nitrogenous Bases - PURINES

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have a double molecular ring of carbon and nitrogen.

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Nitrogenous Bases - The two purines are

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ADENINE and GUANINE

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Nitrogenous Bases – PYRIMIDINES

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have a single molecular ring of carbon and nitrogen.

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Nitrogenous Bases - The two pyrimidines are

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THYMINE, CYTOSINE

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Nitrogenous Bases - A purine always bonds with

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a pyrimidine.

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Nitrogenous Bases - from species to species DNA

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Varies. Chargaff also discovered that DNA of different species differs in its proportions of adenine and guanine meaning the amount of A, T, C, and G in DNA ___VARIES____ from species to species.

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Nitrogenous Bases - Are DNA bases equal in in amount?

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In each species the amount of A EQUALS the amount of T and the amount of G EQUALS C.

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Nitrogenous Bases - What are total number of possible nucleotide sequences per chromosome

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Since any of the four possible nucleotides can be present at each nucleotide position, the total number of possible nucleotide sequences per chromosome is 560,000,000. Humans have 46 chromosomes which results in the incredible possibility of 4140,000,000 nucleotide sequences.

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Nitrogenous Bases - The sequence of bases between the backbones determines

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the GENETIC CODE of an organism.

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DNA Replication - During the phase of the cell cycle called INTERPHASE, DNA

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replicates itself.

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DNA Replication - Steps to DNA replication

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Unwinding, Complimentary base pairing, joining

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DNA Replication – What occurs during the Unwinding Step

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a. An enzyme called topoisomerase UNTWISTS the double helix. b. DNA HELICASE breaks the hydrogen bonds holding the double helix together, “unzipping” it so that half of the nitrogen bases are on ONE side of the ladder while the other half are on the OTHER side of the ladder. c. Each of these sides of the ladder will serve as the PARENT strand in the construction of new DNA.

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2. DNA Replication – What occurs during Complementary base pairing step

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a. An enzyme called DNA POLYMERASE begins assembling nucleotides that are free within the cell to the parent strand. b. DNA polymerase follows the base-pairing rules adding T’s to A’S and G’s to C’S forming a new strand of DNA that is complementary to its parent strand. c. DNA polymerase can attach the nucleotides to the 3 PRIME end of a DNA strand. d. As DNA polymerase matches the nucleotides, it serves as a “_PROOFREADER_” to correct any nitrogen bases aren’t matched correctly.

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DNA Replication – What occurs during the Joining Step of Interphase

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a. An enzyme called DNA LIGASE joins the two segments into a continuous strand of DNA. b. Each of the two strand of DNA now has one PARENT side and one complementary “NEW” side.

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Chromosomes – Are Nuclear packages in which

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GENETIC INFORMATION is stored.

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Chromosomes - DNA wraps around proteins called

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HISTONES to form a chromosome.

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Chromosomes - An individual histone with two coils of DNA wrapped around it is termed

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a NUCLEOSONE

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Chromosomes - When cells prepare for division, chromosomes are duplicated to form

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two SISTER CHROMATIDS.

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Chromosomes - The sister chromatids are held together

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by a CENTROMERE.

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Chromosomes – Do individuals have a different amount of chromosomes?

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Every individual in a given species possess a specific number of chromosomes.

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Chromosomes –The specific number of chromosomes

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occur in virtually every cell of the body.

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Chromosomes - Human body cells have

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46 chromosomes

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Chromosomes - 46 is termed the somatic number for humans because

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It is the amount of chromosomes held by the human body cells.

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Chromosomes – the number 46 is also identified as

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the DIPLOID number (2n)

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Chromosomes – We have two sets of chromosomes. Where do they come from

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One set of chromosome comes from MOM and one set comes from DAD

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Chromosomes - The two sets of chromosomes that code for the same TRAITS are called

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HOMOLOGOUS CHROMOSOMES.

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Chromosomes – Homologous Chromosomes have

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the same length, shape and can be arranged according to size, length, shape, and centromere position.

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Chromosomes - a KARYOTYPE is

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when homologous chromosomes are arranged according to size, length, shape, and centromere position

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Chromosomes – AUTOSOMES

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are chromosomes that are the same in males and females.

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Chromosomes – SEX CHROMOSOMES

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differ between males and females and are used to determine the sex of an individual. In humans:

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Chromosomes – Males have

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XY sex chromosomes

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Chromosomes – Females have

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XX sex chromosomes

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Chromosomes – The number of chromosomes present in the sex cells called

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(GAMETES) is 23. This is the HAPLOID number (n)

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Mutations - DNA polymerase works very quickly and

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sometimes makes mistakes when base-pairing.

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Mutations – When polymerase makes a mistake base pairing it is called

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a MUTATION occurs.

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Mutations – Is a mutation temporary?

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A mutation is a PERMANENT change in DNA.

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Mutations – What mutations may become cancer?

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Mutations that occur in somatic (OR BODY) cells may become cancer.

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Mutations – Can mutations in DNA be passed down?

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Mutations that occur in sex cells can be passed to OFFSPRING.

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Mutations – Some environmental factors that increase the chance for a mutation

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1. RADIATION – XRAY (ultraviolet, gamma, electromagnetic) 2. CHEMICALS both natural and synthetic. Ex: tobacco smoke

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Mutations – SUBSTITUTION

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occurs when one base is substituted for another base.

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Mutations - FRAME SHIFT MUTATIONS

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occur because of insertions or deletions of a base pair again leading to the formation of another protein.

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Mutations - INSERTION

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one or more base pairs become inserted in DNA

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Mutations - DELETION

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one of more base pairs are lost from DNA

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Mutation Effects – Can a mutation be deadly?

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Mutations can alter the DNA and DECREASE the organism’s survival.

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Mutation Effects – Are all mutations “bad”

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Mutations can alter the DNA and have NO EFFECT on the organism and/or INCREASE the chance of the organism’s survival.

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Nucleic Acids - There are two types of nucleic acids

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DNA and RNA

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Nucleic Acids – DNA stands for

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Deoxyribonucleic acid (DNA)

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Nucleic Acids – DNA contains

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the sugar DIOXYRIBOSE

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Nucleic Acids – DNA is ___ stranded

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DOUBLE stranded

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Nucleic Acids - The purpose of DNA

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is to transmit HEREDITARY INFORMATION

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Nucleic Acids -The bases in DNA include

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A T C G

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Nucleic Acids – RNA stands for

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Ribonucleic acid (RNA):

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Nucleic Acids – RNA contains

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the sugar RIBOSE

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Nucleic Acids - RNA is __ stranded

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SINGLE stranded.

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Nucleic Acids - The purpose of RNA is to

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PROTEINS

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Nucleic Acids - The bases in RNA include

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A U C G

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Nucleic Acids - Uracil REPLACES

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Thymine

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Nucleic Acids - Like Thymine, Uracil binds to

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ADENINE

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Nucleic Acids – There are 3 Types of RNA

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mRNA, tRNA, rRNA

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Nucleic Acids – mRNA is the

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MESSENGER RNA and carries the information from DNA (in the nucleus) to the CYTOPLASM

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Nucleic Acids - tRNA is the

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TRANSFER RNA and brings AMINO ACIDS to the RIBOSOMES so they can be assembled into proteins.

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Nucleic Acids - rRNA is the

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RIBOSOMAL—makes up the RIBOSOME (the site of protein synthesis)

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Genetic Expression – Genetic expression is

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The use of genetic information in DNA to make PROTEINS

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Genetic Expression – Occurs through two stages

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transcription and translation

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Genetic Expression – Stage 1

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TRANSCRIPTION - making RNA from DNA

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Genetic Expression – Stage 2

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TRANSLATION - making PROTEINS from RNA

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Genetic Expression - Transcription is the process of

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producing RNA from DNA. (DNA  RNA)

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Genetic Expression - Transcription STEP 1

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mRNA is the form in which information moves from DNA in the NUCLEUS to the ribosomes in the CYTOPLASM

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Genetic Expression - Transcription STEP 2

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RNA then bonds to the PROMOTER - sequences on the DNA to begin the process.

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Genetic Expression - Transcription STEP 3

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RNA HELICASE unwinds and unzips this segment of the nuclear DNA.

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Genetic Expression - Transcription STEP 4

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As the enzyme RNA polymerase moves along the template strand of DNA, complementary RNA nucleotides pair with DNA nucleotides of the template.

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Genetic Expression - Transcription STEP 5

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The RNA nucleotides are joined together in a single string by RNA polymerase only adds it to the 3 ends so it moves 5 to 3 .

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Genetic Expression – Transcription STEP 6

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The mRNA then carries this information to the RIBOSOMES in the cytoplasm and attaches.

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Translation – defined

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The process of converting the information in a sequence of nitrogen bases on mRNA into a sequence of AMINO ACIDS which bound together form a PROTEIN (RNA  PROTEIN)

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Translation - Before translation can be understood

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the Genetic Code needs to be discussed.

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Genetic code mRNA is read in groups of

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three bases each. These three base segments are referred to as CODONS

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Translation – Genetic Code Each codon is the

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GENETIC CODE for an amino acid. Ex: AUG codes for the amino acid methionine.

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Translation – Genetic Code What does CUA code for?

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LEUCINE

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Translation – Genetic Code What does GUA code for?

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VALINE (WILL BE USING CHARTS)

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Translation – Genetic Code AUG is usually considered

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the START codon, beginning the process of translation

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Translation – Genetic Code UAG, UGA, and UAA

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do not specify an amino acid and usually represent as STOP codons.

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Translation – Genetic Code There are 20 naturally occurring amino acids which can be encoded by

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sixty four codons in the genetic code.

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Translation – Genetic Code which RNA contains the Anti-codon

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tRNA carries a molecule referred to as the ANTI-CODON

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Translation – Genetic Code The anticodon is

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a triplet of nucleotides that base-pairs with an MRNA codon.

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Translation – Genetic Code Attached to the other end of the tRNA molecule is

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an AMINO ACID the one specified by the codon—tRNAs with different anticodons carry different amino acids.

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Translation – STEP 1

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mRNA attaches to a ribosome which is made of RRNA and PROTEIN

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Translation – STEP 2

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An INITIATOR tRNA is located in the cytoplasm carries a start amino acid (methionine) to the start codon (AUG) on mRNA.

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Translation – STEP 3

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A second tRNA carrying an ANTI-CODON and an AMINO ACIDE attaches to the second codon on the mRNA.

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Translation – STEP 4

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A PEPTIDE BOND forms between the two amino acids.

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Translation – STEP 5

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The first tRNA is RELEASED and a third tRNA BINDS to the mRNA and the process repeats itself and the peptide chain grows longer and longer until a STOP CODON (UAA, UAG, or UGA) is reached.

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Translation – STEP 6

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The end result is the formation of a PROTEIN

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Gene Control - Cells only use an average of about

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10% of the genes on their DNA at one time.

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Gene Control – do all cells use all the genes?

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Some genes, ALL cells express while other genes are used by only ONE OR TWO types of cells. Think eye color would not be used in the hair color sequence

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Gene Control - DIFFERENTIATION

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is the process by which cells of multi-celled organisms become specialized.

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Gene Control - MASTER GENES

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are genes that encode products that affect the expression of many other genes.

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Gene Control - Expression of a master gene causes undifferentiated cells to differentiate and

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SPECIALIZE to form TISSUE and ORGANS

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Gene Control - Ex: SRY gene is a master gene in males that causes the formation of

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testes. Some cells in the testes make testosterone which contributes to males secondary sex characteristics.

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Epigenetics – METHYLATION

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adding a methyl group (CH3) to histone proteins makes the DNA wrap more tightly around the proteins discouraging TRANSCRIPTION

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Epigenetics - Direct methylation to DNA (not to the histones) is usually a

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PERMANENT manner of suppressing genes. Once a base has become methylated in a cell’s DNA, it will stay methylated in all of the cell’s descendants.

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Epigenetics - Environmental factors including chemicals in CIGARETTE SMOKE can add

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more methyl groups to DNA.

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Epigenetics - Methylation can also occur

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spontaneously during DNA replication.

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Epigenetics Can methylation be passed to offspring?

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methylation is passed on to FUTURE OFFSPRING.

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Epigenetics – What is Epigenetics

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changes in DNA expression that are not a direct change of the DNA is EPIGENETICS

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Epigenetics – which is faster evolution or epigenetics

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Epigenetic inheritance can ADADPT offspring to an environmental stressor much more QUICKLY than evolutionary processes.

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Epigenetics – Are epigenetics the same as evolution?

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Even though epigenetic changes are passed on to offspring, they are not considered evolutionary as the DNA is NOT CHANGED Ex. Nine year old boys whose fathers smoked cigarettes before age 11 are overweight compared with boys whose fathers did not smoke in childhood.