Unit 4: DNA & Heridity Study Guide

Frederick Griffith 1928

Discovered the transforming principle and showed genetic information could transfer between bacteria

Transforming principle

A substance that can transfer genetic information between bacteria

Oswald Avery Colin MacLeod Maclyn McCarty 1944

Identified DNA as the transforming principle responsible for bacterial transformation

Alfred Hershey Martha Chase 1952

Confirmed that DNA not protein is the genetic material using bacteriophages

Rosalind Franklin

Used X ray crystallography to produce Photo 51

Photo 51

X ray diffraction image providing evidence of DNA helical structure

James Watson Francis Crick 1953

Proposed the double helix model and complementary base pairing

DNA

A molecule that contains the genetic code unique to every individual

Genetic code

Information encoded in the sequence of nucleotide bases

Genetic information

Encoded in the sequence of bases and determines traits

Inheritance

Passing genetic information from parents to offspring

Double helix

Two long strands forming a twisted ladder shape

DNA backbone

Alternating sugar deoxyribose and phosphate groups

Nucleotide

Building block of DNA

Three parts of a nucleotide

Sugar deoxyribose phosphate group nitrogenous base

Deoxyribose

Five carbon sugar in DNA

Phosphate group

Links the sugar of one nucleotide to the next

Nitrogenous base

Base component that carries genetic information

Adenine DNA

Base that pairs with thymine

Thymine DNA

Base that pairs with adenine

Cytosine DNA

Base that pairs with guanine

Guanine DNA

Base that pairs with cytosine

DNA base pairing

A pairs with T and C pairs with G

A pairs with T DNA

Forms 2 hydrogen bonds

C pairs with G DNA

Forms 3 hydrogen bonds

Hydrogen bonds

Bonds that hold complementary bases together

Complementary strands

DNA strands run complementary to each other

RNA base pairing

A pairs with U and C pairs with G

A pairs with U RNA

Adenine pairs with uracil in RNA

C pairs with G RNA

Cytosine pairs with guanine in RNA

Uracil

Base found in RNA that replaces thymine

DNA replication

Process by which the genome DNA is copied

Purpose of replication

Ensures each daughter cell receives a complete genome

Replication fork

Y shaped structure where DNA is separated and copied

Leading strand

Synthesized continuously in the 5 prime to 3 prime direction

Lagging strand

Synthesized discontinuously

Okazaki fragments

Short fragments formed on the lagging strand

Termination replication

Process by which DNA replication is completed

Importance of replication

Essential for growth repair and cell division

Heredity

Passing of traits from parents to offspring

Genetics

Study of how genes and traits are passed down

Molecular genetics

Structure and function of genes at a molecular level

Transmission genetics

Patterns of inheritance and gene transfer

Population genetics

Genetic variation within and between populations

Josef Kolreuter

Conducted hybridization experiments observed blending inheritance and noted hybrids reverted in later generations

TA Knight

Crossbred pea plants observed consistent inheritance patterns and laid groundwork for Mendel

Gregor Mendel

Austrian monk who conducted pea plant experiments and founded Mendelian genetics

True breeding

Always passes its characteristics to the next generation

Pea plant advantages

Self pollination easy cross pollination clear contrasting traits

Trait

Characteristic that distinguishes one individual from another

Polygenic trait

Characteristic determined by many genes

Seven pea plant traits

Flower position axial or terminal plant height tall or short pod color green or yellow pod appearance round or wrinkled seed color yellow or white seed appearance round or wrinkled flower color purple or white

P generation

True breeding parent generation

F1 generation

First generation offspring from parent cross

F2 generation

Offspring produced when F1 plants are crossed

Hybrid

Offspring of two different true breeding parents

F2 recessive ratio

Approximately one fourth show recessive trait

3 to 1 ratio

Typical phenotype ratio in F2 monohybrid cross

Law of Dominance

Some traits mask the expression of others

Law of Segregation

Each organism inherits two alleles one from each parent which separate during gamete formation

Law of Independent Assortment

Different traits are inherited independently except in linked genes

Gene

Segment of DNA that codes for a protein and determines a trait

Allele

Different form of a gene

Dominant allele

Always expressed if present represented by capital letter

Recessive allele

Expressed only when two copies are present represented by lowercase letter

Genotype

Genetic makeup of an organism such as AA Aa or aa

Phenotype

Physical expression of a trait

Homozygous

Two identical alleles such as AA or aa

Heterozygous

Two different alleles such as Aa

Punnett square

Tool used to predict genotype and phenotype ratios

Genotype ratio

Ratio of allele combinations in offspring

Phenotype ratio

Ratio of observable traits in offspring

Mendels impact

Foundation of modern genetics influenced chromosomal theory DNA discoveries agriculture GMOs medicine genetic screening and gene therapy

DNA Replication Step 1

Initiation: DNA Helicase unwinds the DNA double helix at the origin of replication.

Creates replication forks where new strands will be synthesized.

DNA Replication: Step 2

Primer Synthesis: RNA primase synthesizes short RNA primers complementary to the DNA template.

Provides a starting point for DNA polymerase.

DNA Replication: Step 3

Elongation: DNA polymerase adds complementary nucleotides to the template strands.

DNA Replication: Leading Strand

Synthesized continuously in the 5' to 3' direction.

DNA Replication: Lagging Strand

Synthesized discontinuously in Okazaki fragments in the 3' to 5' direction. (Always write in the 5' to 3' direction)

DNA Replication: Step 4

Okazaki Fragment Processing: RNA primers are removed by DNA polymerase and replaced with DNA nucleotides.

Gaps between fragments are sealed by DNA ligase

DNA Replication: Step 5

Termination: Replication proceeds in two opposite directions until entire DNA molecule is replicated.

Process completes when replication forks meet or termination regions are reached

DNA Replication: Step 6

Accuracy and Proofreading: DNA polymerase proofreads and corrects errors during replication.

Ensures high levels of accuracy in copying genetic information.

Termination

Process by which replication of a DNA molecule is completed

DNA Helicase

Unwinds the double helix at the replication fork.

DNA Polymerase

Catalyzes the addition of nucleotides to the growing DNA strand.

RNA Primase

Synthesizes short RNA primers necessary for DNA

synthesis.

DNA Ligase

Joins Okazaki fragments on the lagging strand.

RNA primer

Short segment of RNA synthesized by RNA primase,

which provides a starting point for DNA synthesis.

Mutation

A change in the DNA sequence due to errors or

environmental factors, affecting genetic information.

Spontaneous Mutations

Natural errors during DNA replication or repair processes.

External Factors in Mutations

Exposure to mutagens like UV radiation, chemicals, or viruses that increase mutation rates

Types of Mutations: Point Mutations

Single base changes (substitution of

one nucleotide for another)

Types of Mutations: Insertions and Deletions:

Addition or removal of

nucleotide(s), altering gene sequence.

Types of Mutations: Frameshift Mutations:

Insertions or deletions that shift

the reading frame, changing subsequent amino acids.

Genetic Diversity

Mutations contribute to genetic variability within populations.

Disease

Harmful mutations can disrupt gene function, leading to genetic disorders, cancer, or developmental abnormalities.

Cystic Fibrosis

Chronic coughing, wheezing, and lung infections

Difficulty breathing

Autosomal Recessive

Huntington's Disease

Uncontrolled movement, difficulty with memory and learning

Autosomal Dominant

BRCA 1 & 2 Mutations

Linked to increased risk of breast and

ovarian cancers.

Epigenetics

Study of changes in gene expression caused by mechanisms other than changes in the DNA sequence itself. Changing how the genes are used not the genes themselfs.

Epigenetics: Cancer

Epigenetic changes can activate oncogenes or silence tumorsuppressor genes