Genetic Control Flashcards
Cell function & Inheritance
What are the four characteristics of a genome?
1) . Store information (for life functions)
2) . Express info (in the form of polypeptides to direct life functions; basically an on/off switch) ex hormones
3) . Replicate/reproduce themselves
4) . Variation by mutation (ex: mutation)
What are the purine vs pyrimidine bases? Which ones connect?
Purine- Adenine and Guanine
Pyrimidine- Thymine (DNA) or Uracil (RNA) and Cytosine
A and T or A and U
G and C
What is a genome?
An organism’s full set of genes that is needed for day-to-day function of all it’s cells (distributed in chromosomes)
What are the names of the two DNA strands we need for replication?
Coding strand (copied in transcription)
Non sense strand (not copied for transcription)
***Both used for duplication/replication
What are the four steps/stages of DNA replication?
1) . Double stranded DNA unwinds
2) . The junction of unwound molecules is a replication fork
3) . A new strand is formed by pairing complementary bases with the old/complementary strand
4) . Two complete DNA helices are made; each one has one new and one old strand = “semiconservative”
How many pairs of chromosomes make up DNA?
23 (one from each parent)
What is chromatin? What is the process of DNA turning into chromatin?
It is a coiled structure that is made up by packaging DNA, ribonucleic acids, and proteins called histones together. The histones attach to and compress the double-helical strands of DNA. The chromatin then forms bead-like structures called nucleosomes. These nucleosomes fill the cell nucleus.
When chromatin and histones are paired together, what impact does this have on DNA replication?
DNA cannot replicate now; chromatin has to change its structure in order for it to be “accessible”. This is called chromatin remodeling
What is a triplet codon comprised of and what does it equal?
Comprised of 3 bases (A,C,T, G); one codon equals one “word” of protein recipe (equal one amino acid)
What is the RNA start codon?
AUG
What are the three RNA stop codons?
UAA, UAG, UGA
What are DNA mutations and what are the three main types?
Mutations are accidental errors in duplication
1) . Substitution of one base pair from another
2) . Loss or addition of one or more base pairs
3) . Rearrangement of base pairs (which leads to a non functional codon)
What are five factors that could cause DNA mutations?
1) . Spontaneous
2) . Radiation
3) . Chemicals
4) . Environmental agents (ex: agent orange in veterans)
5) . Inherited : only occurs in GERM cells (sex chromosomes)
What is the most critical enzyme for DNA repair? What type of genes controls this enzyme?
Endonucleases because they recognize the mutations, cleave them out, and replace that area with the correct sequences
EN’s are under control of repair genes (loss of these genes makes DNA more susceptible to mutations)
What two type of genes are mutated in cancer?
proto-oncogenes or suppressor genes
What is the variability of each individual’s genetic sequence (compared to the general population)?
0.1% (accounts for physical traits, behaviors, and disease susceptibility)
What part of DNA comes from the mother? What are three characteristics of this DNA
mtDNA
Double stranded ring (instead of double helix), 37 genes, and mtDNA disorders are rare but commonly effect the neuromuscular system (autism might be new link)
What is RNA responsible for?
Key for protein synthesis
responsible for assembly of biochemical products
RNA characteristics: what type of strand, what are its bases, what is its sugar made of, what is it used for, what kind of properties can it have
Single stranded AGCU (uracil) Sugar is ribose Used for gene expression (more unstable than DNA) Can have catalytic properties
DNA characteristics: what type of strand, bases, what is its sugar made of, what is it used for
Double stranded
Bases: AGCT
Deoxyribose
Used for information storage
What are the three types of RNA
Messenger (mRNA), Ribosomal (rRNA), Transfer RNA (tRNA)
What is the function of mRNA? What process is it formed by? What is its relationship with tRNA?
It carries genetic info from DNA to the ribosome for protein synthesis
It is formed by transcription
tRNA recognizes it and allows the ribosome to form the correct polypeptide chain
What is the function of rRNA? Discuss the size of rRNA
Makes up ribosomes which are “workbenches” for translation of mRNA into protein; translates the instructions and provides the machinery needed for protein synthesis
it is the largest RNA molecule
What is the function of tRNA? discuss its size and what are its two recognition sites
reads the mRNA and delivers the appropriate amino acids to the ribosome
smallest RNA molecule
Recognition sites: one is complementary for the mRNA codon and the second is for its particular amino acid
What is RNA transcription? Where does it occur? What enzyme helps generate the mRNA strand?
Synthesis of RNA from a DNA template to make mRNA(coding strand of DNA is used as template)
Occurs in nucleus
RNA polymerase
What two things do you need for effective transcription?
1). RNA polymerase binds with other factors to form transcription complex
2). Transcription complex binds to promoter region of DNA called TATA box
This activity begins replication and will only stop once it hits a stop codon
What happens during RNA processing?
It adds certain nucleic acids to the ends of RNA strands and splices out other internal sequences
What is splicing?
It is part of RNA processing within transcription
Splicing increases the product from one gene, meaning more than one protein can be made from a single gene sequence
What are exons vs introns?
Both are involved in RNA splicing
Exons are the retained piece of protein coding mRNA sequences
Introns are the pieces between exons (that we remove)
What happens when we get mutations at RNA processing splice sites?
Mutations at these sites can cause altered proteins that can result in a diseased state
Where does mRNA go once its processed?
it diffuses through the nuclear pores into the cytoplasm, where it controls protein synthesis (translation)
What are five steps of translation?
1) . mRNA strand starts in the cytoplasm
2) . mRNA binds with rRNA and tells rRNA what order to place the amino acids in
3) . mRNA communicates instructions to tRNA
4) . tRNA delivers the AA to the polypeptide chain and puts it in the right place
5) . New protein is synthesized & folded into 3D conformation
What is gene expression?
It refers to the degree for which a gene or particular group of genes are active:
WHAT polypeptide the genes code for, WHEN that gene is activated or inactivated, and HOW MUCH polypeptide is produced from an activated gene
What is induction vs repression in terms of gene regulation
Induction means gene is turned on (increase of gene expression)
Repression means gene expression is reduced/turned off
What are transcription factors?
They are a class of proteins that bind to their own specific DNA region and increase or decrease transcriptional activity of genes (genes are active/inactive based on tissue type, age, response to environment)
What are two genetic control regions for gene expression?
Promoters and Enhancers
What are promoters in terms of gene expression? Where are the located and what molecule are they recognized by?
regions that initiate transcription
they are located next to their genes
recognized by RNA Polymerase II
What are enhancers in terms of gene expression? Where are they located?
They stimulate transcription and modulate it from a distance
found further upstream than promoters
How many pairs of chromosomes are in the body?
All somatic cells have 23 pairs
22 are autosomes
1 pair is the sex chromosomes (XX or XY)
How many genes does the X chromosome carry?
2000-5000
Females have 2
What information does the Y chromosome carry?
contains genes important for normal male sexual development
What is a barr body?
it refers to the inactive X chromosome in females or males (normal males do not have barr bodies)
What is the Lyon hypothesis?
In females, only one X is genetically active & other is inactivated early in embryogenesis; either X can be inactivated and this is random from cell to cell (inactive X can be from mother or father)
What are the three phases/divisions of interphase (non-dividing phase)? What structure/form is DNA in?
G1 (gap 1)
S phase- DNA is replicated and synthesized, chromosomes are replicated
G2 (gap 2)- volume of cell has doubled, triggers mitosis
DNA is chromatin form
What is mitosis vs meiosis?
Mitosis- replacing non germ cells
Meiosis- replicating germ cells
What are four functions of the Gap phases of the cell cycle during interphase?
Cell growth, differentiation, metabolic activity, protein synthesis
What is the process of mitosis?
First, parent cell (diploid) has two sets of chromosomes and goes through S phase (replication).
Mitosis- chromosomes in this parent cell are then split into two diploid daughter cells
What is the process of meiosis? How many times does this process occur in a cell line?
Replicating germ cells which results in gametes (reproductive cells)
Once
What is the first stage of meiosis?
Stage 1: homologous chromosomes pair up, go through crossing over stage, and then each daughter call contains 1 of each homologous chromosome pair and a sex chromosome
What is the main purpose of “crossing over” in meiosis?
Crossing over increases genetic variety in offspring (usually not shared equally between daughter cells)
What is the second stage of meiosis?
23 chromosomes of each of the 2 daughter cells divide and results in 4 daughter cells
What is a telomere?
region of repetitive nucleotide sequences at each end of a chromatid (which is supposed to protect the end of chromosomes from deterioration)
** there are thoughts that as we age & in cancer, we lose more and more of chromosome until division just stops
What is a gene?
DNA sequence that codes for a polypeptide
What is an allele?
Alternate forms of a gene at the same locus
What is a locus?
Location of a gene on a chromosome
What is phenotype vs genotype?
Genotype: what alleles you carry, your genetic info
Phenotype: what you look like; traits associated with that genotype
What is homozygous vs heterozygous in terms of gene traits?
Homozygous: both chromosomes have the exact same allele (dominant vs recessive traits)
Heterozygous: both chromosomes have a different allele; “carrier”
What is expressivity?
The amount the gene is expressed in the phenotype (can range from mild to severe)
What is penetrance?
ability of the gene to express its function (ex: 75% penetrance means 75% of people with that genotype will present will a recognizable phenotype)
Describe single-gene vs polygenic inheritance
Single-gene: follows mendelian law of inheritance, one pair of genes is responsible for trait
Polygenic: multiple genes at different loci, with each gene exerting a small additive effect in determining a trait
What is multifactorial inheritance?
Similar to polygenic with multiple alleles at different loci affecting the outcome, but has the addition of environmental effects on the genes
(ex: increase risks of having same defect in subsequent pregnancies)
What is epistasis?
One gene masks the phenotypic effects of another non allelic gene (ex: baldness is epistatic to red hair, pt will be bald bc red hair gene is covered up)
Define multiple alleles
More than one allele affects the same trait (ex: ABO blood type)
Define complementary genes
Each gene is mutually dependent on the other
Define collaborative genes
two different genes influencing the same trait interact to produce a phenotype that neither gene could produce alone
What is genetic imprinting
when parental genomes don’t contribute equally in development of an individual (100 genes exhibit this)
-certain disorders vary depending on if it was inherited from mother or father
What is a carrier in terms of mendelian inheritance?
a person who is heterozygous for a recessive trait and does not manifest that trait
What is dominance vs segregation vs independent assortment in Mendel laws?
Dominance- TT x tt = 100% Tt
Segregation- Tt x Tt = 75 % tall & 25% short
Independent assortment - RrGg x RrGg (not focusing on)
What is genomic mapping and what is its purpose
assignment of genes to specific chromosomes or parts of the chromosome
focuses on slight variations in genome that causes susceptibility to disease & responses to microbes/toxins/drugs
How many genes are in the human genome? How many genes have been mapped to a specific chromosome?
30,000
25,000
What are the three methods of genomic mapping?
Linkage studies- assume genes occur in a linear array along the chromosome
Gene dosage studies- measure enzymatic activity
Hybridization studies- uses somatic and in situ hybridization
What is a single nucleotide polymorphism
the site in a DNA sequence where individuals differ by a single base pair
What is a haplotype?
a small variation in a gene sequence that is thought to account for the individual differences in physical traits (also called polymorphisms)
What is a HapMap and what can it tell us?
map of different haplotypes; can give idea of potential risk of disease/type of diseases a person will have during life; help diagnosis & treat disease
What are four types of Recombinant DNA technology?
Gene isolation
Pharmaceutical applications (insulin/HGH)
DNA fingerprinting
Gene therapy
What is gene isolation in terms of recombinant DNA technology?
cut a DNA molecule apart, modify & reassemble its fragments; then produce copies of modified DNA, its mRNA, and its gene product
What is DNA fingerprinting?
detects the slight variations in the genomes of individuals (high accuracy)
What is gene therapy?
inserting genes into multicellular plants and animals; adenoviruses are the best to use
