Human Genome and Gene Expression Flashcards
what type of molecule is a double helix
DNA
what molecule is each human chromosome
a single linear DNA molecule with a string of nucleotides that spell out genes
when was the first full human genome sequenced
in 2003
what does a human genome consist of
around 3 billion basepairs
how many genes are in a human genome
25,000
what percentage of genome is protein coding regions
around 2%
what makes up 50% of a genome
repetitive DNA of truly unknown function
what are polymorphisms
sites in the DNA
what are alleles
different versions or variants of DNA sequences
how much does it cost to obtain one human genome
$1000
what is a gene
the entire nucleic acid sequence
what is the purpose of a nucleic acid sequence
it is necessary for synthesis of a functional polypeptide
what RNA molecules do DNA regions code for
tRNA, rRNA, and mRNA
TRUE OR FALSE: tRNA, rRNA, and mRNA are not genes, but are RNA molecules
FALSE: they are considered genes as well as RNA molecules
where do genes lie amidst
a large expanse of nonfunctional, non coding DNA and genes
what are different versions of genes called
alleles
how much DNA is in each diploid human cell
two meters of DNA in length
how does so much DNA fit into a tiny nucleus
fold with proteins
how big is a nucleus
5 micrometer
how many pairs of chromosomes are in a cell’s nucleus
23 pairs
what are pairs of chromosomes called
homologous chromosomes
what are autosomes
the 22 pairs of chromosomes of homologous chromosomes
what are sex chromosomes
the 1 pair that contains genes which establish gender
what are diploids
somatic cells that have 46 chromosomes
how do diploid cells divide
mitosis
what are haploid cells
germ cells that create gametes that have only 23 chromosomes
how do haploid cells divide
meiosis
what are somatic cells also known as
body cells
what are germ cells also known as
sex cells
what is created by a genotype
a range of phenotypes
what influences phenotypes
the environment
how many copies of each gene do we have
2
what is a dominant allele
a single copy of the allele that is sufficient to manifest the phenotype
what is a recessive allele
an allele that is only manifested when an organism has two of this type of allele
what is homozygous dominant
two dominant alleles
what is homozygous recessive
two recessive alleles
what is heterozygous dominant or simply heterozygous
one dominant allele and one recessive allele
what is a carrier
heterozygote that has a single recessive allele contributing to trait, but since it is recessive the trait is not expressed
what is one-trait cross
considers the inheritance of one characteristic and one gene
how is a allele combination created
one trait cross
what is an example of one trait cross
FF x Ff
what are punnet squares
the use of a grid or matrix to diagram crosses between individuals by using the possible parental gametes
what is the purpose of punnet squares
to figure the probability that an offspring will have a particular genotype and phenotype
what is a monohybrid cross
a punnet square that includes one trait
what is a dihybrid cross
a punnet square that includes two trait
what is complete dominance
dominant allele produces a functional protein which has apparent effects; recessive allele produces a less functional protein and has no apparent effects
what are the three categories dominance
complete dominance, codominance, incomplete dominance
what is codominance
both alleles produce functional proteins and effects of both alleles are apparent in the heterozygous phenotype
what is incomplete dominance
the expression of a trait in a heterozygous individual is somewhere between expression of the trait in a homozygous dominant individual and the expression of the trait in a homozygous recessive individual
what is an example of incomplete dominance
a red rose and a white rose, the next rose would be pink
what is an example of codominance
a red fish and a blue fish would create a red spotted blue fish
what is albinism
the inability to produce melanin
what causes codominance
it occurs when the allels are equally expressed in a heterozygotes
what blood type alleles are codominant
A and B
what blood type alleles are recessive
O
what is a phenotype example of incomplete dominance
sickle cell allele
what is incomplete dominance
expression of the trait in a heterozygous individual is in between the way the trait is expressed in homozygous dominant or homozygous recessive person
what does the allele for sickling hemoglobin produce
an aboral form of hemoglobin that is less efficient in binding oxygen
what are polygenic traits
traits that are often non discrete or continuous aka quantitative traits
what is an example of a polygenic trait
height
what are pleiotropy traits
one gene that contributes to multiple traits
what is a multifactorial trait
a polygenic trait that is also influence by the environment
what are examples of multifactorial traits
skin color, and tanning
what is x-linked inheritance
the allele is carried on the x chromosome
what is y-linked inheritance
the allele is carried on the Y chromosome
TRUE OR FALSE: most sex-linked traits are Y-linked
FALSE it is x linked
TRUE OR FALSE: most sex linked trait are not related to sexual characteristics
TRUE
what is color blindness
most often characterized by red-green color blindness
what is muscular dystrophy
characterized by wasting of muscles and death by age 20
what is hemophilia
characterized by the absence of particular clotting factors that causes blood to clot very slowly or not at all
who are X linked traits and disorders found in
males
why are X linked disorders more often found in males
because recessive alleles are always expressed and males can only be homozygous for x linked alleles
what is mutation
a heritable change in DNA sequence
what time can mutations occur
any time
what are the two types of mutations
gremline and somatic
what are genetic disorders
disease causing alleles autosomal recessive
what is tay-sachs disease
lack of the enzyme that breaks down lipids in cell lysosomes resulting in lipid excess and eventually death in infants
what is cystic fibrosis
ion channel defect, so Cl- ions do not pass normal through a cell membrane resulting in thick mucus in lungs and other places often causing infections
what is phenylketonuria (PKU)
lack of an enzyme needed to make a certain amino acid (tyrosine) and affects nervous system development
what is sickle cell disease
red blood cells are sickle shaped (rather than biconcave) clogging blood vessels and are less efficient at carrying oxygen
what is Huntington disease
huntington protein has too many glutamine amino acids leading to the progressive degeneration of brain cells
what is Marfan syndrome
a genetic disorder that affects the connective tissue. mainly affects the skeletal, cardiovascular and ocular systems
what does DNA stand for
deoxyribonucleic acid
what is DNA
double stranded molecule twisted to form a double helix
what is a nucleotide consist of
one sugar, one phosphate, one nitrogenous base
what are the pairs in a nucleotide
A and T and C and G
how does DNA go to RNA
transcription
how does RNA go to protein
translation
how does DNA replicate
the parental molecule unwinds and unzips,
both parental strands serve as templates for new strands,
free nucleotides link to complementary bases on each DNA strand
what is the function of DNA polymerases
to link sugars and phosphates
what is DNA polymerases
a protein and an enzyme
how does DNA direct cellular activities
DNA codes for RNA, which codes for proteins, and proteins play structural or functional roles in cells
how is a gene expressed
when the protein it codes for is produced
what is RNA
single stranded polymers
what makes up RNA
nucleotides
what’s the backbone of RNA
ribose and suer-phosphate
what are the bases in RNA
A,C,G and U
what are the three main types of RNA
mRNA, tRNA, and rRNA
what is mRNA
messenger RNA
what is the function of mRNA
carries genetic information from DNA to the ribosomes
what is rRNA
ribosomal RNA
what is the function of rRNA
joins with proteins to form ribosomes
what is tRNA
transfer RNA
what is the function of tRNA
transfers amino acids to a ribosomes where they are linked together to make polypeptides or proteins
what are ribozymes
enzymatic RNAs
what is snoRNA
components of mRMA splicing machinery
what is miRNA
microRNAs that regulate gene expressions
what are the two main steps of gene expression
transcription and translation
what is transcription
DNA is read to make mRNA in the nucleus of our cells
what is used to make mRNA
RNA polymerase
what is translation
reading the mRNA to make a protein in the cytoplasm on the ribosomes
what are the three steps of transcription
DNA unwinds, RNA nucleotides pair with DNA bases and are linked together, The RNA transcript is released from the DNA
what is introns
intervening sequences
what are exons
expressed sequences
what modifications to mRNA are made before it leaves the nucleus
removal of introns
what is the role of exons
to direct protein synthesis
what does codon mean
“words” in the genetic code
what are the stop codes for genes
UAA, UGA, and UAG
what is the start code for genes
AUG
what is the function of anticodon
binds to codon on MRNA, following complementary base pairing rules
what is the function amino acid attachment sites
the bind to a specific amino acid
what is the structure of ribosomes
two subunits, each composed of ribosomal RNA (rRNA) and protein
what is the function of ribosomes
bring tRNA bearing an amino acid close enough to mRNA to interact
what is the initiation stage of translation
major players in protein synthesis come together
what is the elongation stage of translation
occurs as enzymes in the ribosome link the amino acids, forming a growing chain of amino acids
what is the termination stage of translation
occurs when a stop codon moves into the ribosome
what is the molecular definition of a gene
a genes the entire nucleic acid sequence that is necessary for the synthesis of a functional polypeptide
what do active genes produce
specific proteins that determine the structure and function of a particular cell
what is heterochromatin
tightly packed chromatin which is not actively transcribed
what is euchromatin
loosely packed chromatin, which is accessible by transcription enzymes
what is epigenetics
the study of heritable changes in gene function which are not controlled by changes in the DNA sequence
what are mechanisms of epigenetics
DNA methylation, histone modifications, chromatin folding
what is an example of epigenetic change
a woman who smokes while pregnant induces epigenetic changes in three generations at once, in herself, her unborn daughter, and her daughter’s reproductive cells
