Biology for Liberal Arts Exam 2, Chapter 7-11

Chapter 7: DNA Structure and Replication, Forensics

Genome

The complete set genetic material encoded within the DNA of an organism

Characteristics of Nucleotides and nucleotide joining

*Each DNA Strand is a chain of nucleotides (sugar, phosphate, and a base)

Nucleotides have 4 Bases= Adenine, Guanine, Cytosine, Thymine

They join together at phosphate groups that form a double helix

Base Pairing Work and how to use it

Only certain nucleotides can pair together due to chemical structures

A always pairs with T

C always pairs with G

Semiconservative model

each newly made DNA molecule contains one original strand and one new strand

Can you be DNA Polymerase?

To build a new strand using complementary base pairing

Human Genome Characteristics

Inherit half from mom and dad

organisms that reproduce sexually pass on hald of their genome to their offspring

Sex Chromosomes facts

XX = female

XY = male

DNA Similarity by family relations

Identical Twins will have a perfectly similar DNA, others will share similar DNA with those in their intermediate family

PCR(Polymerase chain reaction)

At high temperatures DNA will denature (unwind and separate)

Steps of PCR

1. Denaturation: double stranded DNA unwinds and separate into two single strands

2. Annealing: Primers come in and tell the DNA polymerase what sequences to amplify

3. Extensions: DNA polymerase will add nucleotide until you end up with 2 stranded DNA again

Primres

short sequences of DNA that tell polymerase where to bind and where to amplify

STR (Short Tandem Repeats)

involves a repeated unit of 1-6 bases

*# of changes vary in person to person

*STR with. higher # of repeats will have a larger size

Math behind PCR

Power of 2: 2^n

COBIS (Combined DNA Index Systems)

Stores DNA from criminal offenders

Innocence Project

to free innocent, prevent wrongful convictions, fair justice system

Steps for the Central Dogma

DNA→Transcription→mRNA→Translation→Protein

DNA

Deoxyribonucleic Acid: Double stranded sugar phosphate
*Deoxyribose

RNA

Ribonucleic Acid: Single stranded sugar phosphate

*Ribose

RNA Polymerase

makes a new strand of RNA from the DNA Strand

Gene Expression

Regulatory Sequence and Coding Sequence [Follows the Central Dogma Steps]

Regulatory Steps

control timing, location, amount of gene expression

GMO ( Genetically Modified Organism )

organisms where it is deliberate changes have been made to alter their genome

Mutations

permanent change in sequence of DNA due to cells not being able to correct the mistakes when base pairing goes wrong

Types of Mutations

Frameshift
Rearrangement
Point Mutation

Consequences of Silent Mutation

Change in DNA nucleotide base without altering the resulting amino acid sequence of a protein

Consequence of Non-silent

change in protein = high likelihood of disease

Causes for Mutations

Replication
Environment
Inheritance

Effect of most mutations

Most are silent mutations = amino acids don’t change and doesn’t lead to disease
64 codons code for 20 different amino acids (plus stops)

Why is the sickle cell trait still around

it is protective against malaria

Causes of Mutation: Replication

When cell replicates there is a small chance that bases will not pair correctly(mutation)

Causes of Mutation: Environment

Mutagens: many components of the environment, our food, and even our cells can cause mutations

• Radiation: UV radiation and X-Rays

• Chemicals: Pollution and pesticides, smoking, and alcohol, char

• Infectious Agents: Some viruses (Hepatitic)

• Cellular Reaction: Cellular Processes produce mutagenic free radicals

Causes of Mutation: Inheritance

Mutations in the beta-globin gene can be inherited, if from both parents then offspring will have sickle cell disease

Frameshift Mutations

Insertion
Deletion
* both severely modified sequences make the protein not functional

Insertion

insert one or more nucleotides, shifting every codon after the insertion

Deletion (Frameshift)

Delete one or more nucleotides, shifting every codon after the deletion

Rearrangement Mutation

Involves larger portions of the genome

• Duplication

• Deletion

• Inversion

• Translocation

Duplication

Section of DNA is added

Deletion (Rearrangement)

Section of DNA is lost

Inversion

Segment of DNA breaks off and reattaches in reverse order

Translocation

segment of DNA breaks off and reattaches to a different chromosomes

Point Mutation

change in single bases

• No mutation

• Silent Mutation

• Nonsense

• Missense (Conservative and Non-Conservative)

Silent Mutation

the changed base results in the same amino acid

Nonsense

the changed base results in a STOP codon, ending the protein

Missense

the changed base results in a different amino acid

Why does mitosis occur

Embryonic development
cell development
repairing damage tissue

Purpose of Checkpoint

allows cell to pause and repair DNA damage before continuing cell division

*if can’t repair then it will go under apoptosis

Apoptosis

programmed cell death

S Phase

DNA Replication occurs

Phases of Mitosis

Interphase

Prophase

Metaphase

Anaphase

Telophase

Interphase

90% time in this phase, most of which is G1
G1 cells are growing and adding organelles

S Phase = DNA Replication

G2 = chromosomes checked for errors

Prophase

Replicated chromosomes begin to coil|
nuclear membrane degrades
Microtubules fibers will form the mitotic spindle
Microtubules will be used to separate chromosomes

Metaphase

Sister chromatids align in the middle of the cell
Microtubules spindle fibers from opposite ends of the cell attach to the sister chromatids
Replicated chromosomes become aligned next to each other

Anaphase

Spindle fibers begin to shorten
This pulls the sister chromatids apart
Sister chromatids go to separate sides of the cell
Picture using a fishing reel

Telophase

Identical sets of chromosomes at each pole
Microtubules disassemble
Nuclear membrane reforms

Cytokinesis(Mitosis)

Cytoplasm divides
Animal cells cell membrane pinches
Plant cells synthesize new cell wall

What is cancer?

uncontrolled cell growth and division

Metastasis

cancer cells leave their original tumor site and spread through the bloodstream to distant locations

BRCA1 function

Tumor Suppressor Gene: Allowing DNA to be repaired, preventing damaged DNA from being passes to daughter cells

Mutated BRCA1 function

DNA repairs become insufficient, mutations likely to occur, chances of cancer increase

How do conventional therapies target cells

genetically nonspecific, meaning they can harm both cancer and healthy cells
-surgery, chemotherapy, and radiation

How many copies of each gene do we have?

2 copies of genes, one inherited from each parent

• Humans have 46 chromosomes (23 from each parent)

What is an allele

Different version of a gene, can have a small difference in their nucleotide sequence

What are gametes?

reproductive cells (sperm and eggs)

Why are gametes special?

they are haploid and are genetically unique produced through meiosis

Steps of meiosis

Replication
Meiosis I

Meiosis II

Step 1 of Meiosis: similar to S phase

The diploid cell duplicates its DNA

Step 2 of Meiosis: Meiosis 1

Homologous chromosomes pair up
Crossing over
Homologous chromosomes separate

Independent assortment

Step 3 of Meiosis: Meiosis 2

Chromosomes line up in the center of the cells

sister chromatids are pulled apart

nucleo membranes reform

result: 4 genetically unique haploid cells

Why does meiosis generate unique cells

Through Crossing Over/Recombination and Independent Assortment

Male vs. Female

Male: Sperm, Female: Egg
XX = Female
XY = Male,

(regardless of multiple sex chromosomes, eg. XXY, this is still considered male)

Genotype

Genetic Makeup

Phenotype

Observable characteristics

Dominate Allele

Allele that mask a recessive allele

Recessive allele

allele that can be masked by a dominant allele

homozygous

two identical alleles

heterozygous

two different alleles

Haploid

one set of chromosomes (n), 23 in humans

Diploid

two complete sets of chromosomes (2n), 46 in humans

Crossing Over

exchange of DNA segments between maternal and paternal chromosomes

Independent Assortment

Random separation of homologous chromosomes into gametes

Meiosis

cell division producing four genetically unique haploid cells

Fertilization

combination of sperm and eggs to form a diploid cell

Nondisjunction

failure of chromosomes to separate properly during meiosis

Trisomy 21

Having three copies of chromosomes 21, associated with Down Syndrome