Test Review 2 Flashcards
Uses of DNA profiles
- US database contains more than 10 million profiles form 15 specific STR regions (CODIS)
- Likelihood that 2 unrelated individuals have he same SNA profile for 15 STRs is 1 in quintillion
- More than 300 prisoners have been exonerated by the Innocence Project
Pharming
using genetically modified animals to manufacture therapeutic drugs
Transgenic animals
animals that carry one or more genes from a different species
Antithrombin
protein that prevents blood clotting
is isolated from transgenic goats milk
Gene is located on chromosome 1
Advantages of transgenic antithrombin
- larger amounts than from human blood
- consistent supply
- less risk for transmitting infections
- less expensive than cell culture
Protein Structure and Function
structural support (Keratin)
Motility (actin)
Defense (immunoglobulin)
catalyze chemical reactions (enzymes)
Proteins
consist of building blocks of 20 amino acids
amino acids bond together to form linear chains
Amino Acids
have the same core structure but have different chemical side groups
Sequence of amino acids
makes the protein unique
determines how the protein folds into a three-dimensional structure
A proteins shape
(dictated y amino acid side groups) determines its function
Hemoglobin
found in human red blood cells and binds oxygen
consists of 4 linear acid chains
Gene
segment of DNA that contains instructions to make at least one protein
Gene eression
process of synthesizing a protein from the information in the gene
Genotype
the genes that make up an organism
phenotype
physical appearance
expression of an organisms genotype
Antithrombin Deficiency
- inactivates enzymes that promote blood clotting
- genetic-based antithrombin deficiency because both copes of antithrombin genes are defective
Alleles
alternative versions of the same gene that have different nucleotide sequences
Making Transgenic goats
-isolate human gene of interest and insert into genome of goat embryo making a hybrid gene that is part human and part goat
2 parts of a gene
Regulatory sequence
Coding sequence
Regulatory sequence
“on/off switch”
-controls timing, location. and amount of gene expression
Coding sequence
“identical of protein”
determines protein amino sequence
Steps for creating Transgenic Animals
- Genetically engineer recombinant gene
Gene regulatory sequence spliced to Human antithrombin gene coding sequence - Inject hybrid gene into fertilized goat embryo and implant in surrogate goat mother
- Purify antithrombin protein from transgenic milk
GMOs
Genetically Modified Organisms
Gene therapy
technology has also been implemented in humans to cure diseases by replacing defective genes with functional genes
2 Major steps in Gene expression
- ) Transcription
2. ) Translation
Transcription
- copying DNA sequence into complementary messenger RNA (mRNA)
- occurs on a ribosome in cell nucleus
Translation
- using the mRNA sequence to synthesize a protein amino acid sequence
- occurs on a ribosome in cell cytoplasm
Transcription (in detail)
- RNA polymerase binds to DNA regulatory sequence just ahead of gene’s coding sequence
- DNA helix unwinds
- RNA polymerase “reads” the DNA sequence and “transcribes” it into a complementary mRNA
- Same base paring as with DNA replication
- except RNA nucleotides are made with uracil instead of thymine - RNA detaches from DNA reforms double helix
Translation (in detail)
- mRNA leaves the nucleus and attaches to the ribosome in the cytoplasm
- The ribosome “reads” the mRNA and “translates” it into a chain of amino acids
- Amino acids are specified by a sequence of 3 nucleotides called a codon
- Transfer RNA transports amino acids to the ribosome; one end binds to amino acid and other end binds to mRNA codon (via 3 base anticodon)
- The rules by which mRNA codons specify a particular amino acid is called the genetic code
- Protein detaches from ribosome and folds into 3D shape
Genetic Code
Universal and Redundant (multiple codons specify same amino acid
Start Codon: AUG
Stop Codon: UAA, UAG, UGA
Cancer
a disease of unregulated cell division that can lead to formation of tumors
Chemotherapy
Treatment of disease (often cancer) using chemicals
most interfere with cell division
Cell division
-Cell Reproduction
Growth
Embryonic Development
Repair/replacement
Cell Cycle
- Interphase
2. Mitosis and Cytokinesis
Interphase
cell prepares for division
G1
S
G2
G1
cell grows; produces new organelles
S
Synthesis; DNA replicates producing sister chromatids
G2
final preparatory stage for division
Mitosis and Cytokinesis
division phase
- sister chromatids separate at centromere producing 2 identical daughter cell nuclei
- cytoplasm divides inot 2 separate cells
Phases of Mitosis
Interphase Prophase Metaphase Anaphase Telophase
Interphase (before mitosis)
Each chromosome replicates during S phase forming sister chromatids
Chromosomes are uncoiled in nucleus
Prophase
Chromosomes coil
Nuclear membrane disassembles
Mitotic spindle forms (microtubules)
Metaphase
spindle fibers attach to chromosomes at kinetochore
chromosomes line up at the equatorial plate
Anaphase
Sister Chromatids separate at centromere
Chromosomes move to opposite poles
Telophase
Spindle fibers disassemble
Nuclear membrane forms around each daughter nucleus
Taxol
effective against ovarian and breast cancers
derived from the bark of the Pacific Yew Tree (home to Northern Spotted Owls)
Interferes with:
1. The normal organization of microtubules
2. Prevents microtubules from shortening
Cells treated with taxol are unable to pull sister chromatids apart and are arrested in metaphase
Cancer: Uncontrolled Cell Division
- occurs when DNA is damaged
- Mistakes are normally monitored and fixed at cell cycle checkpoints (G2, M, G1) with two outcomes:
1. DNA repair mechanisms fix damaged DNA
2. Apoptosis- programmed cell death - Damage sometimes occurs to DNA coding checkpoint proteins and then cells divide uncontrollably
Cancer Treatments
Surgery
Chemotherapy
Radiation Therapy
Surgery
Removes lump of cells
Chemotherapy
Chemical treatment for metastatic cancers (spread to new location)
- usually interferes with cell cycle
Radiation Therapy
High energy ionizing radiation
-kills dividing cells by damaging DNA resulting in apoptosis
Both Chemotherapy and radiation cause
severe effects by damaging all rapidly dividing cells
Other chemicals to be used to fight cancer
in invertebrate animals like sponges which are sessile (attached to substrate)
First Immortal Human Cell Line
Henrietta Lacks
HeLa Cells
-derived from cervical cancer cells
Mutation
A change in the DNA sequence
Hereditary Mutation (Germ-line Mutation)
-A mutation in a gene inherited from parents ( sperm or egg)
-BRCA 1/ BRCA 2
high risks of developing breast cancer
-Normal BRCA protein regulates the cell cycle
Nonhereditary Mutation (Somatic Mutation)
- A mutation that occurs in somatic cells
- these are nonhereditary cancers
Mutations during DNA replication
About 1 in 10,000 to 100,00 times, DNA polymerase adds the wrong nucleotide during DNA replication
- Enzyme “proofread” and correct mistakes or the cell undergoes apoptosis
- fewer than one mistake in 10 billion nucleotides escape these
Consequences of Mutations
Negative: Spontaneous abortion/ result in disease such as cystic Fibrosis
Positive: Result in some health attribute
ex: Allow blood to carry more O2
How do mutations influence gene expression
Mutations alter DNA sequence
Substitution
Deletion
Insertion
Sickle Cell Anemia
substitution of one nucleotide of the hemoglobin protein gene A for T
Ethnic Groups and Genetic Diseases
Herediatary diseases are oftem more common in certain ethnic groups
- desvend from small groups of people
- populations expand and contract
- intermarry within the population (isolated populations)
Mutagens
- Physical or chemical agents that can damage DNA
- UV light, pollution, char
Carcinogens
Type of mutagen
Any chemical agent that causes cancer by damaging DNA
Alcohol, smoking, pesticides
Two types of Cell Cancer Genes
Proto-oncogenes
Tumor Suppressor Genes
Proto-oncogenes
genes that code for proteins that promote normal cell division
Oncogenes- mutated proto-oncogene that is always “turned on” (accelerators)
Her2- proto-oncogene in breast cancers
Tumor Suppressor Genes
Genes that code for proteins that regulate the cell cycle
-Mutated suppressor genes lose normal function (brakes) Ex: BRCAs 1 and 2
Multiple Hits Model
takes more than a single mutation to cause cancer
- after 1 or 2 hits a benign tumor (noncancerous and does not spread) may form
- after several more hits, a malignant tumor (cancerous and spreads) may result
- Cancer affects peope as they age because their cells accumulate more mutations
- Individuals with hereditary mutations develop cancers at an early age
Cystic Fibrosis
-Most common fatal genetic disease in US
- Due to a mutation in the CFTR gene
-Located on chromosome 7
-Codes for a transmembrane protein
(transports CL- ions)
CF patients
-Thick mucus clogs airways, lungs, and digestive ducts
-susceptible to frequent lung infections
Humans are diploid
2 copies of every chromosome in each of their body cells (somatic cells)
homologous chromosomes
2 paired chromosomes
one is inherited from the mother and one from the father
carry the same genes
alleles differ
Gamete
Sex cells that carry only one copy of each chromosome
Haploid because they only carry one copy of each chromosome
Meiosis
specialized type of cell division generates haploid gametes (sperm and eggs) Sperm (23) Egg (23) Fertilization Zygote (46) Mitosis Embryo
Meiosis consists of 2 separate divisions
- Meiosis I - separates homologous chromosomes
2. Meiosis II - separates sister chromatids (no more reduction of numbers)
Meiosis generates genetic variation in gametes by 2 mechanisms:
Recombination
Independent assortment
Recombinatin
Crossing over
- maternal and paternal homologous chromosomes pair and exchange DNA segments (meiosis I)
- between non-sister chromatids
Independent Assortment
Alleles of different genes are distributed independently of one another (meiosis I)
-2nd possible arrangements (n= haploid number)
Carrier
heterozygous individuals can pass on a recessive gene without showing any of its effects
Huntington’s Disease
caused by a dominant allele
Pre-Implantation Genetic Diagnosis
Detect and select embryos that do not carry defective alleles
Humans have 23 pairs of chromosomes
22 pairs are autosomes
1 pair of sex chromosomes
Males inherit
1 Y from their father and I X from their mother
Females inherit
I X from their father and I X from their mother
The SRY gene
on Y chromosome signal testes to develop
Testosterone
Testes produce
promotes development of male tissue
Ovaries
produce estrogen
promotes development of female tissues
Sex Development Disorders
Intersex occurs when external genitalia don’t match the internal sex organs
Genetic mutations can result in sex development disorders such as
SRY gene mutation (XY but female genitalia)
Androgen Receptor mutations (XY doesn’t respond to male hormones)
Congenital Adrenal Hyperplasia (XX with excessive male hormone production- internal organs are female outside organs are male)
Chromosomal Mutations can also lead to sex development disorders such as
Triple X syndrome (Fertile Female)
XXY Klinefelter syndrome (infertile male)
XYY syndrome 47 (Infertile female)
X turners syndrome (Infertile Female)
Sex linked Inheritance
-Some genetic conditions are more common in males than in females
- Red-green Colorblindness
(7% males and .4% in females)
-Hemophilia (1 in 5000 males worldwide)
- Duchene Muscular Dystrophy (DMD) (1 in 2400 males)
- These conditions are caused by genes located on the x chromosome and are X linked traits
Y-Chromosome Analysis
was used to test the DNA of Thomas Jefferson and Sally Hemings’ descendants
it is possible because Y doesn’t undergo recombination in meiosis
Incomplete Dominance
When heterozygotes have a phenotype intermediate between homozygous dominant and homozygous recessive
Co-dominance
When both alleles contribute equally to the phenotype
ABO blood types
3 possible alleles (A, B, O)
A and B are co-dominant
A and B are both dominant to O
4 phenotype for the human blood ABO type
A, B, O, and AB
Universal recipient AB positive
Universal Donor O negative
Rh factor genes
Rh positive = dominant
Rh negative = recessive
Rh status indicated presence/absence of Rh blood proteins on RBCs
Single trait
determined by more than one gene is reffered to as a polygenic trait
Polygenic traits
show continuous variation in the population -height -IQ -Face shape -Skin color - body size have a quantities effect with polygenes traits there is not two extremes and an intermediate like in codominance - a lot of in between
Multifactorial inheritance
genes and the environment interact to produce a phenotype
Nutrition can influence the expression of genes that determine human height
Depression has also been shown to exhibt multifactorial inheritance (combination of genes plus stressful environment)
Coat color in the Siamese cat is another example of multifactorial inheritance
Thalidomide
drug influencing gene expression
sedative taken during first trimester of pregnancy
results in birth defects and cancers of reproductive organs
Caterpillar morphology
Caterpillars that feed on oak flowers look like oak flowers
caterpillars that feed on oak leaves look like twigs
Serotonin Transporter Function linked depression
Important signaling molecule in the brain
The transporter influences the levels of serotonin available- people with depression have lowered levels of serotonin in spaces between cells
Individuals with 2 copies of short allele and 4 or more traumatic life events more likely to show signs of depression
Depression is
a multifactorial trait
Nondisjunction
failure of chromosomes to separate accurately during cell division (meiosis I or II)
Aneuploidy
abnormal number of on or more chromosomes
Trisomy 21 (down syndrome)
3 copies of chromosome 21 (2n +1) as a woman ages, the risk of Down’s syndrome increases from 1 to 1250 births at 25 to 1/100 at age 40
Patau and Edwards’s Syndromes
3 copies of chromosomes13 and 18
Aneuploidies due to misalignment of chromosomes during meiosis
A man’s age also influences sperm quality
Amniocentesis
technique that removes amniotic fluid to obtain fetal cells
chromosomal makeup of fetal cells can be analyzed using a karyotype
