Test 1 Flashcards
What is the common name of Drosophila Melanogaster?
Fruit Fly
What is the common name of Coenorhabditis elegans?
Roundworm
What is the common name of Arabidopsis Thaliana?
Thale Crest
What is the common name of Mus Musculus?
House Mouse
What is the common name of Zea mays?
Corn
What is the common name of Neurospora Crassa
Bread Mold
What is the common name of Macaca Mulatta?
Rhesus Monkey
What is the common name of Xenopus Laevis?
African Clawed Frog
What is the common name of Rattus Norvegicus?
RAT
What is the common name for Danio Rerio?
Zebra Fish
What are characteristics of a good model organism?
- Small Size
- Controlled breeding- easy to breed to specific individuals
- Raising-Easily raised in a laboratory setting without losing a lot of money
- Biological Knowledge- the more we already know the better
- Genome size- one we have already sequenced or know a lot about
- Interesting, useful and unusual
- Life cycle- Not a long generation time, something we can easily observe
- Ethics- the closer the “model” gets to humans or having human like characteristics, the more problems society will have when it is being used for scientific research
- Liablilities- the fewer the better
Gene (locus)
genetic factor that helps determine a trait, at the molecular level it is the sequence of DNA that is transcribed into an RNA molecule
Allele
One of two or more alternate forms of a gene
Chromatin
material found in the eukaryotic nucleus consisting of DNA and protein; another name fore the DNA after it is packaged to fit into the cell
Chromosome
Structure of DNA and associated proteins that carries one of the DNA molecules
Sister chromatids
The two chromosomes that are attached to the same centromere after replication
Homologous Chromosomes
chromosomes that have the same length, centromere positions and genetic loci, but can have different alleles
autosome
chromosomes that are the same in both sexes
Phenotype
what individual looks like
Locus
position of a gene on a chromosome (loci=plural form)
Genotype
allele composition usually represented by using letter abbreviations for alleles
Sex Chromosomes
differ between sexes
Stages of Mitosis and number of chromatids are attached to the centromere in each stage
Prophase (2)
Metaphase (2)
Anaphase (1)
Telophase (1)
resulting in two daughter cells
Cytokinesis
The division of the cytoplasm
What is the purpose of checkpoints in Mitosis
Key transition points in the cell cycle
What do functional Eukaryotic chromosomes contain?
Telomere
Centromere
At least one origin of replication
Substages of prophase I in Meiosis
Leptotene- chromosomes begin to coil up and chromosomes are visible
Zygotene- Homologous chromosomes synapse
Pachytene- Crossing over occurs between non sister chromatids of homologous chromosomes
Diplotene- homologous centromeres begin to repel from each other
Diakinesis- Terminalization of the chiasmata occurs as homologous centromeres continue to repel
Stages of Meiosis and number of chromatids are attached to the centromere in each stage
Prophase I (2) Metaphase I (2) Anaphase I (2) Telophase I (2) Prophase II (2) Metaphase II (2) Anaphase II (1) Telophase II (1)
4 meiotic products
What are the roles of Cohesin and Shugoshin in mitosis and meiosis?
Cohesin- holds sister chromatids together in mitosis and meiosis. It also acts as chiasmata in meiosis to hold homologs together (different forms of this protein in mitosis and meiosis)
Shugoshin (guardian Spirit)- protects cohesio at the centromere in anaphase I of meiosis, but is degraded by anaphase II. This allows homologs to separate in anaphase I but keep the sister chromatids together.
Comparing Mitosis and Meiosis
Mitosis:
- one division results in 2 daughter cells
- Chromosome number per nucleus maintained in mitotic products
- 1 pre-mitotic S phase per cell division
- Normally, no pairing of homologous chromosomes
- Normally, no cross overs
- Centromeres divide in anaphase
- Conservative process: daughter cell genotypes are exactly like parent cell
- Cell undergoing mitosis can be diploid or haploid
Meiosis
- Two divisions result in 4 products of meiosis
- chromosomes number halved in meiotic products
- 1 pre-meiotic S phase per meiotic process (2 divisions)
- Homologous chromsomes synapse
- Usually, at least one cross over per homologous pair
- Centromeres do not divide in anaphase I but do divide in anaphase II
- Promotes variation among products of meiosis
- Works best with diploid cells
How does meiosis provide variation from generation to generation?
- Crossing over allows each chromosome to contain some maternal and some paternally derived alleles
- Suffling of maternal and paternal chromosomes (independent Assortment)
What studies are important in cancer research?
Cell cycle and regulation studies
Nondisjunction
mistakes in separation of chromosomes in meiosis
Karyotype
an organized array of an individuals chromosomes
When does nondisjunction occur and what happens?
can occur in either the first or second anaphase in meiosis
results in gametes with an abnormal number of chromosomes
Mendel’s law of Random Segregation
- The two alleles of a locus do not blend or fuse
- During gamete formation in a heterozygous individual, half of the gametes will receive one of the alleles and half of the gametes will receive the other allele
- This results in an individual of a genotype Aa producing two types of gametes in equal frequency
Mendel’s law of independent assortment
- During gamete formation in an individual who is heterozygous for two loci, the allele from the first locus that goes into a particular gamete will not influence which allele at the other locus goes into the gamete
- This results in an individual of genotype AaBb producing four types of gametes in equal frequency: AB, Ab, aB, and ab
Product rule and its uses
probability of two or more independent events occurring together is the product of their probabilities.
- clue “and” in a word problem
- P(A and B)= P(A)* P(B)
Addition rule
the probability of two or more mutually exclusive events is the sum of their probabilities
characteristics of a homologous chromosome
same length, centromere position, banding pattern, and genetic loci
What are the two ways that meiosis producing 4 meiotic products?
1) reductional division- number of chromosomes in the daughter cell is half the number in the original cell (one of each homologous pair in each daughter cell)
2) Equational division- number of chromosomes at the beginning and end of the division cycle is the same, but the daughter cell only have one chromatid
What is simple mendelian inheritance?
- one allele is completely dominant to the other (unless otherwise specified in the hypothesis
- Random segregation occurs at all loci involved in the test
- Independent assortment occurs between all loci involved in the test
- Random Fertilization occurred in producing the individuals in the generation that is being tested
Protenor mode of sex determination is?
XX/XO- sexes have a different number of chromosomes
Females have 2 (XX) males have 1 (XO)
ex: grasshoppers, orthoptera
Lygaeus mode of sex determination?
XX/XY- sexes have same number of chromosomes, but one pair doesn’t look homologous
EX: fruit flies, us, mealworm
Heterogametic Sex
XY, XO
Homogametic sex
XX
Hemizygous
one copy of the chromosome is present
crossing bbxbb you get all bb’s
Holandric
only found in the males
Sex determination in Drosophila Melanogaster (fruit flies)
Calvin Bridges: Genic Balance theory
-Sex is determined by the ration of the number of X chromosomes to the number of autosomal sets
Normal Femal= xx/2a ratio of 1.0 Normal Male=XY/2A ratio is .5 below.5= sterile male in between .5-1= interest 1.5-= infertile femtal
Nondisjunction of the X chromosome results in gametes XX and 0. After fertilization, the following aneuploid types are formed. XXX, XXY, and XO, Y0 flies die.
What type of chromosome system does chicken birds and some fish use for sex determination?
ZZ= male ZW= female
SRY GENE
CODES for testis determining factor (TDF) which triggers undifferentiated gonadal tissue to form testis
XO = what syndrome?
Turner Syndrome
XXY= what syndrome?
Klinefelter syndrome
XXX = what syndrome?
Female-variable expression (sterility problems)
XYY= what syndrome?
Male- nondisjunction of Y
Barr Body
inactivated X chromosome
How many Barr Bodies are in a: Normal Female Normale Male Turner Female Klinefelter male
1
0
0
1
What does a diamond mean in a pedigree?
Unknown Sex
What sex is a square?
Male
What sex is a circle?
female
Characteristics of autosomal recessive trait?
- usually appears in both sexes with equal frequency
- tends to skip generations
- affected offspring are usually born in unaffected parents
- When both parents are heterozygous, approximately one-fourth of the offspring will be affected
- Appears more frequently among the children of consanguine marriages
Characteristics of autosomal dominant trait?
- usually appears in both sexes with equal frequency
- both sexes transmit the trait to their offspring
- does not skip generations
- Affected spring break must have an affected person unless they possess a new mutation
- when one parent is affected (heterozygous) and the other parent is unaffected, approximately half of the offspring will be affected
- Unaffected parents do not transmit the trait
Characteristics of X-linked recessive trait?
- usually more males than females are affected
- affected sons are usually born to unaffected mothers; thus the trait skips generations
- approximately half of a carrier (heterozygous) mothers sons are affected
- never passed from father to son
- all daughters of affected fathers are carriers
Characteristics of X-linked dominant trait?
- both males and females are usually unaffected; often more females than males are affected
- does not skip generations. affected sons have an affected mother; affected daughters must have either an affected mother or an affected father
- affected fathers pass the trait on to all their daughters
- affected mothers (if heterozygous) will pass the trait on to half of their sons and half of their daughters
Characteristics of Y-linked trait?
- only males are affected
- passed from father to all sons
- does not skip generations
What is the cause of TFM- testicular Feminization Sndrome
a mutation on the X chromosome the acts only in XY individuals to nullify the effects of the Y chromosome
is X^d Y heterozygous?
Yes
What do genetic counseling sessions discuss?
- Diagnosis/ Genetics/Inheritance of the disorder
- Symptoms and treatment options
- Social and psychological aspects of managing the disorder
- Risks/Likelihood/ of having a child with a disorder
- Arranging for genetic testing
- assisting with counseling and finding support groups to help patients and families cope with stress
- NONDIRECTIVE- try not to tell people what to do but to inform them on info
How do you write genotypes with two X-linked loci?
X^(hC)Y for males
X^(Hc)X^(Hc) for females
What are some common reasons for seeking genetic counseling?
- a person knows of a genetic disease in the family
- a couple has given birth to a child with a genetic disease, birth defect, or chromosomal abnormality
- a couple has a child who is mentally retarded or has a close relative who is mentally retarded
- an older woman becomes pregnant or wants to become pregnant. There is a disagreement about the age at which a prospective mother who has no other risk factor should seek genetic counseling; many experts suggest that nay prospective mother age 35 or older should seek genetic counseling
- Husband and wife are closely related
- A couple experiences difficulties achieving a successful pregnancy
- A pregnant woman is concerned about exposure to an environmental sub stand (drug chemical or virus) that causes birth defects
- a couple needs assistance in interpreting the result of a prenatal or other test
- both prospective parents are known carriers for a recessive genetic disease
What are some form of genetic testing done during prenatal?
- Ultrasound
- Amniocentesis
- CVS
- Fetal Blood Sampling (needle into umbilical cord)
- Maternal blood screening tests
- Preimplantation Genetic Diagnosis (in conjunction with in virto fertilization)
How is newborn screening done?
A blood sample is taken from a heel prick just after birth
-if you catch early on some intervention can have higher quality of life
Is there anything done about privacy and genetic discrimination?
Genetic Information Nondiscrimination Act (GINA)- health insurance companies and employers cannot discriminate based on the results of genetic tests, nor can they require genetic testing
Complete dominance
one allelic form is expressed (the dominant form) and one is not seen (recessive form)
Dominance
interaction between alleles
Incomplete dominance
phenotype of the heterozygote is intermediate between phenotypes of the two homozygotes
Recessive Lethal
two copies of the allele are required to result in death of the individual
Dominant Lethal
death occurs if an individual has only one copy of the allele. Only see if individual survives long enough for phenotypes to be seen and only passed on to progeny if individual surveys to reproduction. (EX: huntington’s Disease)
Anticipation
Increasing severity or earlier age of onset as trait is passed from one generation to generation
Multiple alleles
more than two forms of the same gene each capable of producing a different phenotype
Penetrance
the percent of individuals of a given genotype that show some degree of expression of that genotype
Expressivity
The range of expression of a genotype
What are some factors that influence phenotypes for a given genotype?
- modifying genes
- enviromental effecting including
- location on the chromosome
- temp
- nutrition
- light
- imprinting
Pleiotropic effects
one gene has an effect on several seemingly unrelated aspects of an individuals phenotype (one gene affects the phenotype of several unrelated traits)
hypostatic
suppressed gene
epistatic
gene that masks the action of another gene
Epistasis
expression of alleles at one locus masks or modifies the expression of another alleles at another locus
interaction between 2 different genes, not interaction between alleles at one locus
Single Recessive Epistasis
the homozygous recessive condition at one locus masks or modifies the expression of alleles at the second locus
Single Dominant Epistasis
Dominant allele at one locus masks or modifies the expression of alleles at a second locus
Duplicate recessive epistasis
identical phenotypes are produced by both homozygous recessive genotypes so a different phenotype is produced only there is at least one dominant alleles at each locus
Duplicate Dominant epistasis
Having at least one dominant allele at either locus results in the same phenotype. The different phenotype is produced when the homozygous recessive occurs at both loci
Duplicate genes with cumulative effect (duplicate interaction)
two genes results in the same phenotype if a dominant allele is present at only one of the two loci. The interaction between dominant alleles at both loci results in a second phenotype and the homozygous recessive condition results in a third phenotype.
Dominant/Recessive Interaction
Dominant and Recessive Epistasis
Dominant at one locus and/or homozygous recessive at the other locus results in one phenotype
Epistasis vs. Dominance
Epistasis- is the interaction between products of different genes
Dominance- is the interaction between different alleles at a particular gene
H substance with ABO type
individuals who are genotypes hh do not make the H substance and cannot produce functional A and B blood antigens. Their blood type is functionally Type O even though this may not agree with their genotype at the ABO locus.
Sex-limited
Autosomal characteristic that is expressed in only one sex or the other
Sex-influenced
autosomal trait that can be expressed in either sex but is more frequent in one sex than in the other
Genetic Maternal Effect
The phenotype of the offspring is determined by the mother’s genotype and not its own genotype
Extranuclear (Cytoplasmic) inheritance
Genes are located on mitochondria or chloroplast DNA and generally are passed from only maternal parent
In what organisms does Haplodiploidy occur? and explain what haplodiploidy is.
Happens in Bees, wasps, hymenoptera
- appears that males are haploid and females are diploid.
- Females must be heterozygous for a single multiple allele locus
EX: mate S^aS^b x S^c
Progeny S^aS^c(female), S^bS^c(female), S^a (male), S^b (male)
Environmental sex determination (Crepidula Fornicata example)
Crepidula fornicata- a marine mollusk commonly known as the slipper Limpet
-live in stacks
-Males are on top and females are on bottom
-Sex can change during the life of the limpet
example of sequential hermaphorditism
What is sequential Hermaphroditism?
each animal can be both male and female, but not at the same time
Sex determination in isogametes? and what is an example of an isogamete?
Chlamydonmonas
mating occurs between +/- isogametes
Cytoplasmic Male sterility?
Corn
IF someone has sex chromosomes XX and one of the x’s has a SRY gene then what sex is it?
xx male
If some has sex chromosomes XY and the Y has a SRY gene on it then what sex is it?
Normal XY male
If someone has sex chromosome XY and the Y is missing the SRY gene then what sex is that person?
XY female
Lyon Hypothesis for Dosage Compensation
inactivation of an X chromosome occurs randomly in somatic cells at some point in development. Once inactivated, all progeny cells have the same X inactivated. The inactivated X is called BARR BODY
This means that females are a mosaic for traits not eh X chromsome
Incomplete dominance
phenotype of heterozygote is intermediate between homozygotes
mating purple and white
(half of the progeny is violet)
Codominance
Heterozygote expresses both alleles as distinct gene products
Phenocopy
an environmental agent mimics a genetic condition
Give examples of a phenocopy
EX: eyeless flies in Drosophila melanogaster can be due to the genotype ee. This condition can also occur to E_ flies if the larvae are exposed to SODIUM METABORATE
PHOCOMELIA in humans results in short, flipper-like limbs and can be inherited as a very rare recessive mutation. The use of THALIDOMIDE by pregnant women can also cause this disorder.
Genome Imprinting
expression of a gene depends on whether it is inherited from the maternal or paternal parent.
Epigenetics
Heritable changes in gene expression without changes in DNA sequence
Endosymbiotic Theory for Organelle origin
Possible origin of organelles is that they were distinct bacteria like organisms that became incorporated into primitive eukaryotic cells
-symbiotic relationship developed through evolution so that each became dependent on other to survive
Snail shell coiling orientation
Maternal Effect
D=dextral d=sinistral
Genotype of mother dictates progeny phenotype by determining orientation of the spindle fibers in the first cleavage of fertilization.
Cytoplasmic inheritance
due to genes on mitochondrial or chloroplast DNA
- Generally one parent contributes almost all of the cytoplasm to the zygote so traits show uniparental inheritance (usually mom gives cytoplasm)
- differences in reciprical crosses
Human mitochondrial disorders suspected if
- observe maternal inheritance pattern
- Disorder related to deficiency in bioenergetic functions of cell
- document a specific mutation in a mitochondrial gene
EX. MERRF, LHON, KSS
What is the statistical or genetic conclusion if your chi square value is less than table value?
fail to reject hypothesis
The data for (trait name) in (organism) is consistent with (the type of genetic inheritance) at the 5% significance level.
What is the statistical and genetic conclusion if your chi square value is more than table value
Reject the hypothesis
There is enough evidence at the 5% significance level to conclude the (trait name) in (organism) is not (type of inheritance)
How to state hypothesis for chi-square
The mode of inheritance for (trait name) in (organism) is (type of inheritance)
incomplete dominance (partial dominance) vs. Codominance
incomplete occurs when the heterozygous individual is phenotypically intermediate to the two homozygous forms, but only one gene product is formed
codominance occurs when the heterozygous individual expressed both genotypes
When does maternal effect occur?
when the mother’s nuclear genotype dictates the phenotype of all the progeny (snail coiling direction)
When does cytoplasmic inheritance occur?
genes located on the mothers mitochondria or chloroplasts dictates the phenotype of all of her progeny
Contrast between cytoplasmicinheritanceand maternal effect
In cytoplasmic inheritance, the presence of all types of mitochondria in a cell can lead to variability in her progeny. Would not expect in traits controlled by maternal effect.
Characteristics of a good model organism?
Small
-easy to breed specific individuals
-easily raised in a laboratory setting without costing a lot of money
-The more we already know the better
-one we have already sequenced or know a lot about
-interesting, useful, and unusual= Armadillo: identical tetrads, Xenopus: Huge oocytes
Short generation time
purpose of mitosis?
process of nuclear division
