Bio 111 Unit 3 (Genetics)

Gene

unit of DNA that determines a trait

Genetic Disease

disease caused by mutation in DNA that is passed from parent to offspring

Sickle-Cell Disease

Mutation in gene that codes for protein on red blood cells changes shape of RBCs from concave disc to a sickle; sickle shape leads to myriad health problems due to low access to oxygen

Red Blood Cells

deliver and exchange gases to body tissues

Hemoglobin

protein complex composed of four polypeptide chains (globins); up to 250 million hemoglobin molecules per RBC

Circulatory System

Heart pumps blood around body vessels to transfer oxygen to tissues

Arteries

Vessels where blood is moving away from heart

Veins

Vessels where blood is moving towards the heart

Heart Structure

Humans have four chambered hearts; right side; deoxygenated blood, left side; oxygenated blood

Blood Pathway

1. Deoxygenated blood enters right atrium on return from body

2. Deoxygenated blood enters right ventricle

3. Deoxygenated blood is pumped to the lungs

4. Oxygenated blood returns to left atrium from lungs

5. Oxygenated blood enters left ventricle

6. Oxygenated blood is pumped through the Aorta to body from left ventricle

Heart Beat (Lub)

Ventricles contract to pump blood out of heart

Heart Beat (Dub)

Atria contract to pump blood to ventricles

Blood Pressure

measures force on artery walls when your heart is beating or between beats

Respiratory System

Gases diffuse across cell plasma membranes according to concentration gradients

Hemoglobin & Gas Exchange

Sickle-Cell Hemoglobin is misfolded, changing shape of cell, losing affinity for oxygen

Anemia

suite of symptoms caused by chronic low oxygen in body tissues

Health Consequences of Sickle-Cell

Pain in joints, enlarged spleen, blocked capillaries in kidneys, reduces immune function

Human Genome

46 chromosomes arranged in 23 pair; 22 pairs of autosomes, 1 pair of sex chromosomes

Diploid

Two copies of each gene; one copy from each ploidy

Sex Chromosomes (F)

Females typically have two X chromosomes

Sex Chromosomes (M)

Males typically have one X chromosome and one Y chromosome

SRY Gene

Confers male typical proteins development

Turner Syndrome

XO; affects 1/2000 females and causes cognitive difficulties and heart defects

Klienfelter Syndrome

XXY; affects 1/500-1000 males and causes infertility

XYY Syndrome

affects 1/1000 men; makes men very tall and muscular

XXX

affects 1/1000 females; hyperfeminine features

Androgen Insensitivity

XY but no testosterone receptor; develop typical female genitalia

Intersex

Reproductive anatoym does not fit definition of male or female; 1/2000-4000

DNA Replication Step 1

Initiation: Begins at origin of replication

DNA Helicase

Binds to DNA and breaks Hydrogen bonds between base pairs; forms replication fork with two separate strands

DNA Replication Step 2

Elongation: A primer of complementary RNA bases binds to each strand; Removed at the end of replication and replaced with DNA

Leading Strand

Strand of DNA synthesized continuously in the 5’ to 3’ direction during DNA replications

Lagging Strand

DNA strand created during replication, shown by discontinuous synthesis in the opposite direction of the moving replication fork

Okazaki Fragments

Short, newly synthesized DNA segments created discontinuously on the lagging strand during DNA replication

RNA Primers

a short, single-stranded segment of RNA, typically 10–12 nucleotides long, that acts as a necessary starting point for DNA synthesis

DNA Replication Step 3

Termination; RNA primers are removed and replaced with complementary DNA bases, Okazaki fragments are sealed together with DNA Ligase

Fixing Replication Errors

1. Proofreading by DNA Polymerase

2. Mismatch Repair

3. Nucleotide Excision Repair

Proofreading

DNA Polymerase proofreads and corrects errors during replication

Mismatch Repair

Occurs after replication; proteins detect, remove and replace incorrect base

Nucleotide Excision Repair

Require for more complex mistakes; DNA is unwound and the incorrect bases, along with bases on 5’ and 3’ ends are removed and replaced

DNA Helicase

Binds to DNA and breaks Hydrogen bonds between base pairs

DNA Polymerase

adds new nucleotides; proofreads errors during replication

Telomerase

an enzyme that extends the telomeres at the ends of chromosomes allowing cells to divide indefinitely

Transcription

Converts DNA to RNA; RNA is transcribed from DNA, both ate nucleotides

Translation

Convert RNA to protein; translates nucleotide language into protein language; different types of molecules

Transcription Step 1

Initiation; DNA double helix is partially unwound at site of transcription; creates transcription bubble

Promoter

Tells enzymes how much to transcribe its corresponding gene

Transcription Step 2

Elongation; RNA Polymerase builds an RNA strand that is complementary to the template strand in the 5’ to 3’ direction; identical except all Thymines have been replaced with Uracils

Transcription Step 3

Termination; specific DNA sequences tell RNA Polymerase to stop transcribing and detach from the DNA template

Translation

converting RNA into protein; occurs in ribosomes in cytoplasm and rough ER; requires free amino acids, ribosome units, transfer RNA

Translation Transfer RNA (tRNA)

Binds the free amino acids to each other in the growing polypeptide (protein) chain; each amino acid type has its own tRNA molecule

Translation Step 1

Initiation; start codon on mRNA recognized by tRNA; tRNA binds to ribosome subunits; ribosome assembles around mRNA

Translation Step 2

Elongation; ribosome “reads” the mRNA, tRNA molecules carrying amino acids bind to ribosome; once amino acid has bound, tRNA detaches from ribosome

Translation Step 3

Termination; stop codon in mRNA reached; ribosome releases both mRNA and newly formed protein; mRNA is degraded to recycle nucleotides

DNA to RNA Sequences

T to A; A to U; C to G; G to C

Structure of DNA

Double helix wraps around histones to form nucleosomes; nucleosomes fold into chromatin; chromatin folds into chromosomes

Meiosis

produces haploid gametes; divides cell chromosome number in half

Fertilization

fusing of haploid gametes to form a genetically distinct, diploid zygote

Meiosis I

The homologous pairs seperate

Meiosis II

In the second division of meiosis, the sister chromatids separate; results in four haploid cells, each just one copy of each chromosome, rather than a homologous pair

Mitosis

Separates sister chromatids; each new cell has two copies of each chromosome

Prophase II

Chromosomes in daughter cells condense; spindle forms

Metaphase II

Sister chromatid pairs line up at the center of the cell

Anaphase II

Sister chromatids are pulled apart by the spindle fibers towards opposite cell poles

Telophase II and Cytokinesis

The nuclear membrane reassembles around the chromosomes; the two daughter cells punch into four daughter cells

Recombination/Crossing Over

Prophase I; Homologous chromosomes pair up and exchange segments of DNA

Synapsis

Pairing of Chromosomes

Tetrad

Set of 4 Homologous Chromosomes

Mitosis Cycle

IPMAT; makes two identical daughter cells; happens in ALL body cells

Meiosis Cycle

IPMAT I & II; makes four genetically different cells; happens in gametes only

Spermatogenesis

Produces four functional sperm cells; happens once puberty has begun

Oogenesis

Produces one functional egg cell; begins when female is fetus, ends after fertilization

Why go through the effort of sexual reproduction?

Increases genetic variation, eliminates bad mutations

Heredity

passing of characteristics from parent to offspring through genes

Johann Gregor Mendel

First to identify the predictive power of inheritance using pea plants

Blending Inheritance

Offspring are a mix of parents

Mendel’s Experiment

Mendel crossed true-breeding purple-flower plants with true-breeding white-flower plants; all offspring in first generation were purple (F1)

Law of Segregation

Each parent puts into