Module 1 Part B: Cell physiology and genetics Flashcards
what are genes?
basic units of inheritance
What are genes composed of?
Composed of sequences of DNA and proteins
What are the four nitrogenous bases in DNA?
Adenine, cytosine, guanine and thymine.
What is a nucleotide?
A DNA subunit, consisting of one deoxyribose molecule, one phosphate group and one base.
How many different types of amino acids does the body have?
20
what are the three stop codons?
UAA
UAG
UGA
What is DNA polymerase function?
A protein enzyme that assists in DNA replication to ensure complementary base pairing of the nucleotides.
what is one single strand of DNA referred to as?
A template (guide)
what is mutation?
an inherited alteration of genetic material that occurs in DNA or mRNA sequence of nucleic acids.
what is base pair substition (form of mutation)?
one base pair is replaced with another
what is a missense mutation?
when one base pair alters a single amino acid
what is a nonsense mutation?
when the substitution produces any of the three stop codons
what is a frameshift mutation?
this involves the insertion or deletion of one or more base pairs in the DNA molecule.–can result in a premature stop codon and greatly alter the amino acid sequence.
What causes mutation?
coping errors during cell division, UV radiation, chemical toxins, viruses.
what kind of mutation is insertion?
one or more bases are added to the DNA strand (may be previous replication of previous base/codons).
where does transcription occur?
In the nucleus
what are the two processes involved in protein synthesis?
transcription and translation
Name RNA’s codon bases?
Uracil instead of thymine
adenine, cytosine, guanine
What is the difference in structure between DNA and RNA?
DNA structure is a double helix; RNA structure is a single strand.
where does translation occur?
In the cytoplasm
How many homologous chromosomes pairs does a human have?
22 pairs
How many sex chromosomes does a human have?
1 pair
What is the female sex chromosome?
XX
What is the male sex chromosome?
XY
how many possible codons are there?
64
what are germline cells?
sperm or egg cells (gametes)
what are somatic cells?
all human cells aside from sex cells
Can mutations in germline cells be transmitted to the next generation?
yes
Can mutations in somatic cells be transmitted to the next generation?
NO
Each somatic cell has how many chromosomes in its nucleus?
46 chromosomes; 23 pairs of chromosomes
how many homologous pairs are there?
22 pairs are the same/identical
what is a karyotype?
a profile of a person’s chromosomes
what is a centrome?
Located where the two pairs of chromosomes attach.
what is an allele?
an alternative form of a gene that is located at a specific position on a a specific chromosome.
Homozygous alleles are :
alike/identical; have the same trait and the same place on the chromosome
Heterozygous alleles are :
different/not the same on the chromosome
what is chromosomal nondisjunction and what is it associated with?
It is an error in which sister/homologous chromatids fail to SEPERATE normally during meiosis or mitosis. This is associated with aneuploidy.
What is a phenotype?
physical characteristics of a gene
what is a genotype?
the genetic makeup/composition of an organism
In which three chromosomes do trisomy occur and is viable for birth?
chromosome 13, 18, and 21.
In which chromosome does Down’s syndrome occur in and which aneuploidy is it associated with?
21st chromosome and it is associated with trisomy.
In which chromosome does Turner’s syndrome occur in and which aneuploidy is it associated with?
45X chromosome, associated with monosomy. Affects females.
Describe the alleles in Huntington’s disease
The alleles are heterozygous which means one allele is normal and one is abnormal
what is mosaicism?
It is the presence within an individual of 2 or more population of cells that differ in chromosomal numbers, usually caused by nondisjunction.
Occurs early in fetal development
what is the chromosomal abnormality with Klinefelter syndrome?
(XXY) an extra X chromosome in males
Mosaicism is sometimes seen in this.
What causes Cri du chat syndrome?
This is caused by a chromosomal deletion.
what is chiasmata and in what part of the cell cycle does it occur?
The exchange of genetic material, referred to splitting or crossing over. Occurs in Meiosis I.
In what order for DNA replication is the strand read?
It reads from the 3’ (prime) end to the 5’ (prime) end.
The antisense strand is use for what an how is it read?
It is transcribed to make mRNA. Reads from 3 prime to 5 prime.
what is transcription?
It is the process during which DNA sequence of a gene is copied to make an RNA molecule. Occurs in the cytoplasm
what is translation?
Process during which an mRNA molecule is used to assemble amino acids into a polypeptide chain.
T or F: Germline mutation can be passed onto descendants.
True
T or F: Somatic mutations can’t be transmitted onto descendants.
True
What is an important difference between mitochondrial DNA and Nuclear DNA?
Mitochondrial DNA is more susceptible to damage than nuclear DNA
Why is pleiotropy?
The genetic effect of a single gene on multiple phenotypic traits. The gene codes for a product that is used by various cells or it has a signaling function on various target cells.
Short answer: one gene has multiple functions that can affect different cell functions.
What is polygenic inheritance?
The influence of 2 or more that are required to express the trait.
( doesn’t follow recessive/dominant traits, example human skin color)
What is penetrance?
It is the possibility that a person with the genotype will exhibit the expected trait.
What is expressivity?
Refers to the ability of a gene mutation to produce different clinical s/s in individuals.
Ex. Cystic fibrosis—can cause infertility in males, some may have severe pancreatic problems while other have severe lung problems
What is incomplete penetrance?
The person may or may not exhibit the characteristic.
What is reduced penetrance?
Occurs when the individual has the genotype for the disease but doesn’t exhibit characteristics at all. (Still can pass the disease on, example retinoblastoma)
What is Age-dependence penetrance ?
Don’t exhibit s/s until adulthood.
Autosomal dominant gene
What is a disease example of age dependence penetrance?
Huntington’s disease
In which direction is mRNA read?
From 5’ prime to 3’ prime
what are introns?
noncoding sections of DNA between genes. They’re a gap in DNA. Introns are not included in mRNA.
What is the start codon for DNA?
AUG (methionine)
Describe the “P” region on a chromosome
Short arm of the chromosome, usually above the centrome. Think P for petite.
Describe the “Q” region on a chromosome
Longer arm of the chromosome, usually below the centrome.
Describe monosomy
When one single chromosome is lost
Give an example of monosomy and what is wrong with the disease
Turner’s syndrome ; affects primarily women as they only have one X chromosome, genotype 45X.
What is trisomy?
Three copies of a chromosome
Give an example of trisomy and describe what is wrong with the disease
Down’s syndrome; there are three copies of chromosome 21.
What is the order for Mitosis?
Interphase, Prophase, Metaphase, and Telophase
What phases consist of Interphase?
G0, G1, S phase, and G2 phase
what happens in Interphase: G1 phase?
growth of cell and preps for cell replication
what happens in Interphase: S phase?
DNA replication/synthesis occurs
What happens in Interphase: G2 phase?
Additional protein synthesis, basically ensure DNA replication from S phase was done correctly. This is before the next phase of mitosis.
M phase is also referred to as :
Mitosis
What significantly happens in Prophase?
DNA has been duplicated, nuclear envelope disappears. Centrioles move to opposite sides of the cell, chromatids form.
What significantly happens in Metaphase?
Chromosome pairs align at the midline, microtubules form and the centrioles pull at the chromosomes at the midline. (THINK metaphase=middle)
What stop significantly happens in Telophase?
Nuclear envelope forms, chromosomes uncoil. Cytoplasm organelles divide into 2 new cells.
what happens in Meiosis I?
germ cells (sperm or ova) replicate and divide so that the daughter cells only has 1 representative of each chromosome pair
In females when does Meiosis II begin?
It stops in Meiosis I and doesn’t go to Meiosis II until ovulation.
what is chiasmata?
exchange of genetic material, usually occurs in Meiosis I. Referred to as “crossing over”
What is X inactivation?
Occurs in females, one of the sex chromosome (XX) is inactivated
what are the DNA base pairs?
Adenine with Thymine
Cytosine with Guanine
what direction is DNA read?
3 prime to 5 prime
In DNA replication/duplication what direction is DNA constructed in ?
5 prime to 3 prime
what is the sense strand of DNA?
Contains the blueprint for protein synthesis
what is the antisense strand?
It is the foundation or template for transcribing mRNA that directs protein assembly for amino acids.
what’s important to know about mitochondrial DNA?
passed from the mother to offspring
more susceptible to damage than nuclear DNA
what are introns?
They are sections of DNA between genes that contain bases that do not code for a polypeptide
Describe a deletion mutation
One or more bases are dropped out of the DNA strand
Pork insulin differs from human insulin in:
Only differs by 1 amino acid on the B-chain, alanine is substituted for thymine
Beef insulin differs from human insulin in:
Has 3 base differences, 2 on the a-chain and 1 on the b-chain
What is an important difference in mitochondrial and nuclear DNA ?
Mitochondrial DNA is more susceptible to damage than nuclear DNA
What is an example of protective polymorphism?
HIV (human immunodeficiency virus)
What is an example of an X-linked recessive disorder?
Hemophilia A, usually receives it from their mother, occurs in males
What protein is associated with hemophilia A?
Factor 8 (VIII) protein deficiency; needed for blood clotting
What is the main electrolyte affected in cystic fibrosis?
Chloride, chloride is secreted instead of being reabsorbed loss of salt
What does the CFTR protein do?
Serves as a channel for chloride and helps regulate sodium
What is the protein used in cystic fibrosis?
CFTR
Cystic fibrosis transmembrane regulator
What are the s/s of tay-Sachs disease?
It’s a progressive disease, child can become deaf, blind, unable to swallow, and paralysis.
Cystic fibrosis is in relation to which chromosome?
Chromosome 7.Q 31.1
What is tay-Sachs disease?
Beta-hexosamidase A deficiency; this enzyme catalyzes the biodegradation of acidic fatty materials known as gangliosides.
(Side note: autosomal recessive disorder, both parents are carriers)
What type of gene disorder is Tay Sachs disease an example of?
A single gene disorder
Beef insulin differs from human insulin by how many and by which chain?
Beef insulin differs from human insulin for a total of 3 based. 2 bases on the A chain and 1 base on the B chain
What base is substituted for pork insulin?
Alaine is substituted for thymine
Pork insulin differs from human insulin by how many amino acids and on what protein chain?
It differs from human insulin by only 1 amino acid and it is on the B chain.
What is an intron?
A non-coding segment spliced out of mRNA.
What is an Exon?
A segment of mRNA that codes for proteins
How many chromosomes does a somatic cell have?
23
People who have down syndrome have a higher risk for developing what disease because of the involvement of chromosome 21?
Alzheimer’s disease
People who have the chromosomes 47, XXY karyotype have what kind of syndrome?
Klinefelter syndrome
What is interchanging of genetic material between non-homologous chromosomes?
Translocation
Describe monosomy
One chromosome and somatic cells has only one copy instead of the normal two copies
Describe trisomy
Chromosomes in somatic cells have three copies instead of the normal two
In proteins synthesis, what comes first transcription or translation?
Transcription comes first then translation
How many chromosomes does a diploid cell have? How many chromosomes does a haploid cell have?
Diploid has 46 chromosomes; haploid cell has 23 chromosomes
What is polyploidy?
A condition in which cells have more than two copies of each chromosome
What is nondisjunction?
An error during cell division in which homologous chromosomes or sister chromatids f
FAIL to separate normally.
What chromosome is associated with Prader-Willi syndrome?
It is caused by Chromosomal Deletion on the chromosome 15, which is inherited from the father.
What is imprinting?
Gene silencing on one copy of a chromosome (but not on the other depending which parent transmit the chromosome. )
Simply: transcriptionally silenced
If a deletion occurs on the chromosome 15 from the mothers the child will develop what?
Angelman syndrome
