Final Flashcards
(91 cards)
1
Q
Functions of the cell
A
- Nucleus: where the chromatin is located, contains the nucleoli which synthesizes ribosomes
- Cell membrane:allows for things to diffuse into and out of the cell, has channels and membrane receptors
- Chromosomes: are made from condensed chromatin, carry genetic information that determines structure, shape, and functions of the cell
- Mitochondria: energy transformation, carry genetic information
- Ribosomes: protein synthesis, synthesizes polypeptides
2
Q
Types of Cells
A
- somatic: most human cells, carry 23 pairs or 46 chromosomes
- adult stem cells: stem cells recovered from bone marrow and other organs of adults
- multipotent: can only form one or a few different cell types
- induced pluripotent stem cells: adult stem cells that can be reprogrammed by gene transfer to form cells w/most developmental potential of embryonic stem cells
- embryonic stem cell: cells in the inner cell mass that of early embryos that will form all the cells, tissues, or organs of the adult
3
Q
Differentiated v Undifferentiated
A
- somatic cells are differentiated
- all other are undifferentiated
4
Q
Stages of the Cell Cycle
A
-G1: growth after initial division, makes the components of the cytoplasm like the various organelles, membranes, and ribosomes
-Mitosis: takes less than an hour; when a complete set of chromosomes is distributed to each daughter cell
G2: the cell is preparing to divide, by the end of this stage the cell is ready to divide, mitochondria divide, precursors of spindle fibers are synthesized
-S Phase: a copy of each chromosome is made, DNA replication, formation of sister chromatids
-G0: inactive state where the cell is not dividing
5
Q
Purpose of Mitosis
A
To create genetically similar cells, which replace other existing cells
6
Q
Apoptosis
A
Programmed cell death
- if it happens to little we would have connected fingers and toes
- if it happens too often cancer could occur
7
Q
Male v Female Gonads
A
- w/in the gonads, cells produced by meiosis mature into gametes and by fertilization gametes from two parents become a zygote
- males: testes produce spermatoza; spermatogenesis begins at puberty at takes about 48 days
- females: ovaries produces oocytes; meiosis 1 begins at embryonic development and ends at ovulation; gametes stay in meiosis 1 until puberty; meiosis takes between 12 and 50 years
8
Q
Ways to generate genetic variation in meiosis
A
- random assortment occurs in meiosis 1 (puts random combination of chromosomes into gametes
- crossing over occurs in metaphase 1
9
Q
Meiosis
A
- genetic variation
- 2 cell division
- 4 daughter cells
- genetically different daughter cells
-1/2 the amount of chromosomes compared to parent - produces gametes
for males, happens in puberty - for females, they are born with their eggs
- purpose is to make gametes
10
Q
Mitosis
A
- create genetically same cells
- 1 cell division
- 2 daughter cells
- same genetic daughter cells
- same amount of chromosomes
- all cells undergo
- happens all the time
- purpose is to replace cells
11
Q
Spermatogenesis
A
- produces 4 daughter cells
- it begins at puberty and continues throughout life
- produce thousands/millions each meiotic event
- produce endless gametes through life
12
Q
Oogenesis
A
- produce two daughter cells and 2 polar bodies
- daughter cells are very large
- begins at birth and doesnt complete meioses 2 until fertilization, lasts 12-50 years
- only produce the number born with
13
Q
What stage of embryonic development are cells taken to create embryonic stem cells?
A
The blastocyst stage: around day 5, before implantation on the uterine wall
14
Q
Assisted Reproductive Technologies
A
- the collection of techniques used to help infertile couples have children
- IUI: sperm injected into uterus
- ICSI: sperm injected right into egg
- IVF: grow embryo outside of mom and later implant
15
Q
Why are egg donors paid more than sperm?
A
- eggs are bigger
- there is an age limit for the women who can donate
- the number of eggs women have is finite
- the process of taking eggs from a female is more invasive than taking sperm from a male
16
Q
Ethical issues with ART
A
- multiple births
- increased transmitting genetic defects to children
- preimplantation can cause parents to be selective about their children’s traits
17
Q
Mendel’s Law of Segregation
A
only one of the two genes is put into a gamete; at fertilization, each offspring will receive one allele for each gene from each parent
18
Q
Mendel’s Law of Independent Assortment
A
- each allele pair segregates into gametes w/o being influenced by the manner of segregation of other allele pairs
- the random alignment of chromosomal pairs in metaphase of meiosis accounts for this law
19
Q
Single-gene trait
A
- one gene controls the phenotype
- widow’s peak, ear lobes
20
Q
Autosomal Recessive Inheritance Patterns
A
- two affected parents=affected offspring
- crossing two heteros leads to 25% chance of affected offspring
- relatively equal ratio of females and males
- relatively rare
- affected individuals have unaffected traits
21
Q
Autosomal Dominant Inheritance Patterns
A
- every affected individual has an affected parent
- equalish ratio between males and females
- two affected could have unaffected
- mostly hetero and homo rec spouse
- phenotype more severe in homo dom than hetero
22
Q
Alter expected phenotypic ratios
A
- incomplete dominance: when the dominant allele does not completely mask the expression of the recessive allele (1:2:1)
- codominance: in a heterozygoye both alleles are fully expressed; (blood types: A,B are dominant-AB is codominant -O is recessive
- epistasis: when there is an interaction of another gene that interferes with the expression of the genes you are looking at (one gene stops the other)
23
Q
How can an autosomal dominant trait skip a generation?
A
- most affected people are heterozygotes thus they can have an unaffected child
24
Q
How can a common recessive trait appear to be dominant?
A
- there is a chance the trait will enter the pedigree from outside the family,
25
Two people expressing the same autosomal recessive trait will have a child that expresses the dominant
there may be different mutations in different genes that control the same things
parents- AAbb X aaBB
child- AaBb
26
Pattern of inheritance from a trait caused by a mutation in mitochondrial DNA
The trait would be passed down from mothers to all offspring. Males would not pass on this trait because there is no mitochondria in the sperm
27
Bombay Phenotype as an example of epistasis
- when mutated it can block the expression of phenotypes A and B
- the second gene is H, which is an encoding to the enzyme that controls the upstream step or the intake of the proteins
- individuals that are completely recessive are not able to place the precursor on the A and B red blood cells
28
Chocolate Lab Puppies as epistasis
- black is dominant, chocolate is recessive
- melanin makes the color
- need dominant for color and placement into the hair
- yellow labs have no melanin but they have coloring in their skin which is dominant but recessive in the expression of the hair
- two genes are interacting to make the phenotype
29
Multifactoral v Polygenetic Traits
- m: traits that result from 1 or more environmental influences and two or more genes
- p: traits that result from 2 or more genes
30
Discontinuous v Continuous
- d: variations are phenotypes that fall into 2 or more distinct, non-overlapping classes; affected little by the environment
- c: distribution of phenotypic characters that are distributed from one extreme to another in an overlapping or continuous fashion, very influenced by environment
31
Heritability
- the proportion of the total phenotypic variation in a population that is due to genetic factors
- variation of visible traits based on genes
32
How to measure heritability
- observe the prevalance
- separate genetic factors from the environment by using ht genetics as a constant and control the environment
- look at comparison b/w families
33
Limitations of heritability
- does not tell us how much of a trait is genetically determined
- even when heritability is high, environmental factors can influence a trait
- heritability is not fixed for a trait, it may be different for a different population and/or a different environment
34
Eye color v height
eye color is more heritable b/c height is more easily affected by the environment
35
Twin studies
- twin studies look at concordance between MZ and DZ
| - if MZ twins are reared apart you can see the effects of the environment
36
Twin study limitations
- twins are usually adopted into similar SES families
- stronger maternal influences in MZ
- MZ are treated more similarly
- lump all MZ together and all DZ together
- assumes that all traits are simple
37
SNP analysis and GWAS to identify genes in polygenetic traits
- SNP's look at the single changes in the nucleotide sequence
- GWAS sees all the individual differences in the sequence and tries to draw conclusions and sees relationships b/w where the changes are
38
Why do clubfoot and cleft palate support the threshold model
- they are both distributed discontinuously but are multifactorial
- individuals w/genotypes that raise liability above a certain genetic threshold will develop the disorder if exposed to the proper environmental conditions
39
How is it possible for a familial trait to have a small genetic component
- shared environments take on parents and family's habits, eat the same foods, live in the same SES
- emotional, economic, physical, and the entire environment that will enhance a small genetic trait or component in a family
40
Difficulties of determining if intelligence is genetically based
- relative combination of genetics, environment, social, cultural influences can't be measured
41
Nondisjunction
- when the chromosomes or sister chromatids don't separate correctly in meiosis. If it occurs, than there will be extra or too few sex chromosomes
- meiosis 1: 2n + 1 and 2n - 1 daughter cells
- meiosis 2: n + 1, n - 1 daughter cells
- mitosis 1: 2n + 1 or 1 = 2n - 1, the new cell will be either trisomic or monosomic
42
Monosomy
- a condition in which one member of a chromosome pair is missing, having one less than the diploid number (2n-1)
43
Trisomy
- a condition in which one chromosome is present in 3 copies, whereas all others are diploid (2n+1)
44
Chromosomal Conditions
- XY: genetic male
- XX: genetic female
- XYY: meta males
- XXY: Klinefelter (male are sometimes sterile)
- 0Y: embryonic lethal
- X0: Turner (sterile female)
- XXX: triple X
- >XXX: poly X (female retardation)
45
Definitions
- chromosomal: chromosomes are XX or XY or any of the above combinations
- genetic: XX and XY
- gonadal: if there is an SRY gene that will code for development of male or female
- phenotypic sex: the sex that is exhibited by the individual
46
SRY gene
- this gene is responsible for male sex determination in humans
- it can only be found on the Y chromosome
- it turns on the genes that promote male development
- it turns off the genes that promote female development
47
XY female or XX male
- androgen insensitivity causes testosterone that would be receipted to not be read and for gonads not to develop
- mutations can cause pseudohermaphroditism (intersex) where an individual has both phenotypic expression of sex
48
X-inactivation
- occurs when either the maternal or paternal version of the x chromosome in a female is silenced in a random fashion
- it is a mosaic of expression of the male or female versions
- calico cats: their fur color is caused by being heterozygous for either (O) black or (o) orange
- when a certain X is turned off, you can see the differences in colors of the fur and thus the mosaic of the random silencing of X's
- the x shuts off when still an embryo
49
How is a girl born to an unaffected male and an unaffected female have mild DMD?
- parents: mom is heterozygous and dad has unaffected
- they each pass on Xs, daughter gets mom's recessive and dad's unaffected
- thats expressed in the child because of the mosaic of expressed X's on the body
50
Sex Linked Traits
-traits only expressed in one sex over the other because of genetic makeup
51
Sex Influenced and Sex Limited Traits
- the sex of the individual effects whether the trait is expressed and to the degree to which the trait is expressed
52
Sex Limited Traits
- genes that produce a phenotype in only one sex
- traits expressed only in females because males die before birth (ex. male lethal X linked dominant traits)
- traits expressed only in males (ex. duchenne muscular dystrophy: males do not have offspring and don't pass their X onto their daughters
53
Genomic Imprinting
- imprinting is physically turning off parts of chromosomes
- the imprinting in males and females is different
- certain genes from mom and dad can be turned off depending on which parent your chromosome section is turned off, it influences what is expressed
- shuts off when still an embryo
- which parent you inherited the particular turning on/off gene determines your phenotype
54
Why do babies conceived via ART have a higher risk for Beckwith Syndrome
- activating the Igf2 gene simulation growth in kids do that they are a lot larger than their peers, ART increases the risk of having Beckwith b/c ART helps couples having problems with conceiving
- the problem could be because of the stimulation of Igf2
55
MAOA gene and aggression
- there is a lack of definitive measurement for many behaviors
- the search for correlations between thousands of genes and thousands of traits and disorders is prone to false positives
56
Two approaches behavioral geneticist use to determine whether there is a genetic explanation for a behavioral trait
- model organisms such as mice are used to study genes, mice share 90% of their genes with humans, BUT mice are not as complex as humans and have different social structures and environments
- twin and adoption studies have issues with controlling environment: adoptive families tend to be well educated and have higher SES
57
Single-gene neurological disorder
-Huntington's Disease is a neurological genetic disorder that affects muscle coordination and leads to mental decline and behavioral symptoms
58
Evidence that supports a role for a single gene
Transgenic mice: the gene for HD was put into the mice and the effects were seen and used the comparative approach to compare the observations in the mice to learn more about the disease and how it works in humans
59
Genetic and/or environmental contributions to traits between twins with only 40-60% concordance
- indicates that there is genetic and environmental contributions to these traits
- they are polygenic and multifactorial
60
Hardy-Weinberg
- assumptions: population is large, no genotype is better than the other, mating is random, mutation and migration or factors that can change allele frequencies do not exist
61
Allele frequency
- the frequency with which alleles of a particular gene are present in a population
62
Phenotypic frequency
-the frequency stating the number of times a specific phenotype occurs in a population in a single generation
63
Genotypic frequency
-the frequency with which certain genotypes appear in a population
64
Apply the Hardy-Weinberg
- p+q=1
| - p^2 + 2pq + q^2 = 1
65
Why a recessive allele can cause a severe disease might be maintained in a population
parents that are not affected but are carriers will pass the alleles to their offspring
66
Why would analyzing mtDNA or Y chromosomal DNA is not effective
- mtDNA is passed on from mothers to all their offspring
- you do not have a clear picture while looking at mtDNA and Y chromosome because of mutations, migration, and different environments
67
There is no meaningful genetic definition of race
- variation in the human genome is continuously distributed, and there are few sharp boundaries separating populations
- most genetic variation is widely clustered and its continental distribution roughly corresponds to traditional racial classifications
68
How does 6ft of DNA fit into the tiny nucleus of each of our cells
- the double helix shape
| - multiple levels of extensively coiled DNA which wraps twice around the histones
69
Parts of a DNA nucleotide
- nitrogenous base
- sugar
- phosphate
- 5' end
- 3' end
70
In what direction does DNA polymerase build DNA
- the enzyme DNA polymerase reads to nucleotide sequence of the template strand and inserts complementary nucleotides in a 5' to 3' direction to form a newly synthesized strand
71
Why is DNA synthesis considered semi-conservative
- only one strand is conserved in each new molecule and one new strand is synthesized
- if DNA is unwound, each strand can serve as a template for making a new complementary strand
- DNA replication provides each daughter molecule with one old and one new synthesized strand
72
Biochemical property of histones to help them bind to DNA
- contain a large proportion of positively charged amino acids
- histones form disc-like structures around which portions of the DNA wrap itself to form structural units (nucleosomes)
73
Heterochromatin
- chromatin can fold upon itself to compact the nucleosomes forming a highly condensed structure
- in the condensed heterochromatin structure, promoter regions are largely inaccessible to transcription factors, hence protein production is inhibited
- metaphase
74
Euchromatin
- this more relaxed chromatin structure whose structure exposes the promoter regions of particular genes that need to be transcribed at specific times and under specific conditions during the lifetime of a cell
- interphase
75
"Every gene has a control panel and a coding sequence"
- control panels contain instruction to tell the cell how to switch genes on or off (start or stop codons)
- coding sequences have information for specific amino acids
- three groups of nucleotides is called a codon, which code for the amino acid
- there are 3 that do not code (stop codons)
- AUG (start codon)
76
Similarities of DNA and RNA
- both made up if monomers called nucleotides
- adenine, cytosine, guanine
- C pairs with G in both
- both are necessary when making proteins
- both have pentose sugar
77
DNA
- stores RNA and protein-encoding information, and translates info to daughter cell
- double stranded
- very stable
78
RNA
- carries protein-encoding info, and translates info to daughter cells
- single stranded
- not stable
79
Classes of RNA
- mRNA: carries genetic information into the cytoplasm-which will be encoded into the sequence of amino acids
- tRNA: brings amino acids to the mRNA ribosome complex during translation; each tRNA molecule has two attachment sites (a nucleotide sequence of 3 nucleotides called an anticodon which pairs with a complementary codon sequence in mRNA; and a site for attachment of the amino acid specified by the mRNA codon)
- rRNA: the site of polypeptide synthesis-during translation the rRNA in the large subunits acts as an enzyme linking amino acids together to form a polypeptide
80
Two major information transfer processes involves in gene expression and where they occur
- nucleus: transcription regulation determines which genes are transcribed and determines availability of mRNA to ribosomes
- cytoplasm: translation regulation determines the rate at which proteins are made and the availability of the finished proteins
81
Which direction does RNA polymerase build RNA?
- builds RNA in a 5' to 3' direction by moving 3' to 5' on the DNA sequence
- RNA polymerase is attached to a promoter
- start: in a stage called initiation, RNA polymerase and several regulatory proteins bind to a specific nucleotide sequence (promoter) that marks the beginning on a gene
- stop: when the RNA polymerase reaches the termination sequence (3' end), it stops adding nucleotides to the pre-mRNA and falls off the DNA template strand; the pre-mRNA molecule is released and the DNA strand re-form a double helix
82
Modifications of pre-mRNA
- removal of introns to generate a coding sequence that can make an amino acid chain
- a nucleotide cap is added at the 5' end for ribosome binding
- a poly-A tail is added at the 3' end for mRNA stability
83
Most of the genes encoded in the nucleus of each of the cell are much larger than the corresponding mRNAs found in the cytoplasm.
- the genes in the nucleus have introns in them, these do not code for amino acids, and they have exons. In mRNA it can take from the same gene strand but use different exons to make different forms of a protein
- nucleus: a poly-A tail is added to many maturing mRNAs; when poly-A tails are made longer, there is increased translation, when producing more protein molecules per mRNA
- cytoplasm: enzymes can lengthen or shorten the poly-A tail; when poly-A tails are shortened, translation of proteins from those mRNAs is decreased
84
How does the ribosome know where to start translation? Stop?
- start codon (AUG)
| - stop codon (UAA, UAG, UGA)
85
How can a human cell create over 1 million different kinds of proteins
- the large pre-mRNA precursor molecules are processed in the nucleus to remove introns
- nucleotide sequences present in genes that are not translated into amino acids, introns are between exons which are DNA sequences that are transcribed joining other exons and translated into the amino acid sequence of a protein
- as introns are removed, the exons are spliced together to form mature mRNA molecules
86
3 billion base pairs in the human genome encode for 21,000 protein coding genes
- many non-coding RNAs exist
| - RNAs that don't code for proteins but play important roles in how genes are expressed
87
What are microRNAs and how do they regulate gene expression
- cellular RNA fragments prevent the production of a particular protein by binding to and destroying the messenger RNA that would have produced the protein
- derived from transcribed single-stranded RNA that folds back upon itself forming double-stranded regions in the molecule
- remaining single-stranded regions are removed by an enzyme creating a double-stranded RNA of 21-22 nucleotides bound to the proteins
- microRNA/protein complex binds to all mRNSs with a complementary sequence, cleaving the mRNA or blocking ribosomes from loading onto the mRNA
88
Alternative Splicing
- exons can be retained or removed during splicing, allowing mature mRNAs to contain different combinations of exons
- allows one gene to encode info for several different forms of a protein
- smooth-muscle mRNA or striated-muscle mRNA
89
Steroids regulate gene expression
- steroid hormones can affect target cells by other means that binding to the "classic" steroid receptors that control gene expression
- they can affect cellular processed more directly by binding to receptors in the plasma membrane of cells; these receptors influence metabolic processed directly, w/o involving gene expression
90
What type of cells would you expect steroids to be able to behave as transcription factors to turn on genes?
hair, skin, red blood cells, sex cells
-each cell type in the body has its own control mechanisms that determine which genes are able to respond to the presence of the sterois
91
Negative feedback loop
- a regulatory mechanism in which a stimulus causes an opposite output in order to maintain an ideal level of whatever is being regulated
- cortisol turns off the gene that signals for the production of more cortisol
