Genetics exam 1 Flashcards
define the principle of random segregation
different alleles for a particular gene occupy the same locus on homologous chromosomes
a cross between two parents that differ in a single characteristic is called?
a monohybrid cross
What is a gene?
a genetic factor that helps determine a trait. DNA that is transcribed into RNA.
What is an allele?
one of two or more alternate forms of a gene
What is a locus?
specific place on a chromosome occupied by an Allele
This term defines a set of alleles possessed by an individual organism
Genotype
Heterozygotes can be defined as?
an individual organism possessing two different alleles at a locus
An individual organism possessing two of the same alleles at a locus
homozygote
The appearance of a given trait
phenotype
Oculocutaneous albinism type 2 is due to a defect in the OCA gene on which chromosome?
Chromosome 15
A genome is defined as a ?
complete set of genetic instructions for any organism either RNA or DNA.
This subdivision of genetics encompasses basic principles of heredity and how traits are passed from one generation to the next.
Transmission Genetics
This subdivision of genetics concerns the chemical nature of the gene itself and how genetic information is encoded, replicated, and expressed.
Molecular genetics
This subdivision of genetics explores the genetic composition of groups of individual members of the same species and how that composition changes geographically and with the passage of time. It is fundamentally the study of evolution.
Population Genetics
Genetic information travels from different parts of the body to reproductive organs (gemmules)
Pangenesis
Inheritance of acquired characteristics proposes?…
acquired traits become incorporated into hereditary information.
ex: the blacksmith’s skills and upper body strength will be passed to his offspring.
miniature organisms that reside in sex cells, and all traits are inherited from one parent is the concept of?
Preformationism
When genes blend and mix
Blending inheritance
The Germ-plasm theory explains that?
all cells contain a complete set of genetic information
All life is composed of cells, and cells arise only from cells relates to which theory?
cell Theory
Traits are inherited in accord with defined principles describes this concept?
Mendelian Inheritance
The nucleus is present in Prokaryotic cells. T/F
false, the nucleus as well membrane bound organelles are absent.
the short arm of a telocentric centromere is identified as? the long arm as?
short arm= p arm
long arm= q arm
a diploid organism has two sets of chromosomes organized as?
homologous pairs
the stable ends of a chromosome
telomeres
a constricted region of the chromosome where the kinetochores form and the spindle microtubules attach
centromere
This cellular process results in an increase in cell numbers and resulting daughter cells that are genetically identical
Mitosis
Interphase has two checkpoints before mitotic division occurs. where are they?
G1-S checkpoint, cell is committed to dividing after this checkpoint
G2-M checkpoint, the cell can begin division
a non-dividing phase in interphase
G0
DNA synthesis, chromosome replication, inactive cdc2 kinase, B(M) cyclin concentration begins to increase at the end of this phase
S phase
activated MPF in this phase leads to activities necessary for mitosis
G-2 phase
Prior to S phase of the cell cycle, each chromosome consists of this many chromatids?
1 chromatid
After S phase of the cell cycle, each chromosome consists of this many chromatids?
2- bound by a centromere
in this phase, the nuclear membrane disintegrates and spindle microtubules attach to chromatids.
Pro-metaphase
in this mitotic phase, the chromosome number has doubled and they have lined up along an equatorial plate
metaphase
If cytokinesis does not occur there may be still be two nuclei, but they will be located in a single cell. resulting in an increase in ploidy. this is called?
Endomitosis
in this phase, S cyclins bind to inactive cdc2 kinase and the cell is in growth and development
G-1
these cells spend more time in the G-1 stage and grow and become differentiated. examples: hematopoietic cells, epithelial cells in the gut lining and the epidermis
Labile cells
skeletal muscle cells, cardiac muscle cells, and neurons are classified as?
non-dividing cells
the fusion of hapoid gametes
fertilization
separation of sister chromatids occur in this stage of Meiosis. EQUATORIAL division.
Meiosis II
separation of homologous chromosome pairs and REDUCTION of the chromosome number by half occurs in this stage of meiosis
Meiosis I
pairing of homologous chromosomes is a major event in meiosis. this is celled?
Synapsis
IF Crossing over happens in this stage of mitosis, where segments of non sister chromatids are exchanged.
Prophase I
Independent assortment produces variation without?
crossing-over
What are the five stages of Prophase?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
when the synaptonemal complex forms because of the synapsis of homologous chromosomes (bivalents) the cell is in this stage of prophase?
Zygotene
chromosomes are threadlike and begin to condense and become visible. The cell is in this stage of prophase?
Leptotene
crossing-over begins and chromosomes become shorter and thicker
Pachytene
Crossing-over continues and the Chiasmata is well-defined.
Diplotene
when Crossing-over is completed and the nuclear membrane is disrupted, the cell is in this stage of prophase?
Diakinesis
whats a Tetrad?
closely associated four sister chromatids of two homologous chromosomes
when the kinetochores face opposite poles, the cell is in?
Metaphase II
the end result for this stage is four genetically unique haploid daughter cells
Telophase II
This protein holds chromatids together during early parts of mitosis and Meiosis.
Cohesin
Cohesin at the centromere is protected by?
Shugoshin
this enzyme breaks down Cohesin at the end of metaphase
Separase
this protein keeps Separase inactive during interphase and early mitosis.
Securin
Monopolins are proteins that keep sister kinetochores oriented (away or towards) the same pole during metaphase I?
toward
Does random distribution of maternal and paternal chromosomes occur in Meiosis II?
no, only Meiosis I
oogenesis results in __ female gamete and spermatogenesis results in ___ male gametes
1,4
Primary spermatocytes are haploid or diploid?
Diploid, they undergo meiosis I to produce haploid secondary spermatocytes.
Spermatids differentiate into?
sperm
Primary oocytes become locked in this stage of Prophase I?
Diplotene
in most mammals, the egg is ovulated at this stage?
metaphase II
up to three haploid small cells are each ootid (a haploid egg) can occur. these are known as?
Polar bodies
the gametophyte stage in plants have a multicellular ___
haploid
the Sporophyte stage in plants have a multicellular ___?
diploid
two defective copies of the MC1R allele results in a person having this?
red hair.
the Melanocortin-1 gene is located on this chromosome in humans
Chromosome 16
increase in the production of Eumelanin gives offspring this hair color?
black or brown
what is Pisum sativum?
the friggin Pea Plant!
Mendel referred to the traits that appear unchanged in the heterozygous F1’s as?
Dominant
traits that disappeared in the F1 heterozygotes were termed?
recessive
when two different alleles are present in a genotype, only the trait encoded by one of them- the dominant allele-is observed in the phenotype
The concept of dominance
Monohybrid crosses are explained by?
the principle of segregation
what is Mendel’s first law?
principle of segregation
Walter sutton contributed the?
chromosomal theory of heredity
this man observed that each pair of homologous chromosomes consist of one maternal and one paternal chromosome and showed that homologous chromosomes segregate independently into gametes in meiosis
Walter Sutton
Segregation results from?
the separation of homologous chromosomes in meiosis
if no crossing-over takes place, the two chromatids of each chromosome segregate into anaphase II and are?
identical
Independent assortment is which of Mendel’s law?
the second law
the key indicator “and” is most likely this rule when you calculate independent probabilities
Multiplication rule
The probability of any two or more mutually exclusive events is calculated by adding the probabilities of these events. Key indicators= “either” and “or”
Addition rule. yay you!
a cross between an F1 genotype and either of two parental genotypes is a?
backcross
a cross between an individual of unknown genotype and a homozygous recessive individual is a?
test cross.
Dihybrid crosses illustrate this second mendelian law?
Principle of Independent assortment
the Chi-square Goodness of Fit test indicates the probability that the difference between the observed and expected values is due to?
Chance
Expected values are obtained by?
multiplying the expected proportion (%) by the total (#)
ex: 3/4 x 150= 112.5
genotypic and phenotypic ratios are identical for?
incomplete dominance
the production of both male and female gametes in the same individual.
monoecious
the production of either male or female gametes in the same individual
Dioecious
male and female sex determination is a characteristic of?
sexual phenotype
both sexes in the organism describes this?
Hermaphroditism
in the ZZ-ZW system, males express?
ZZ-homozygous
birds, snakes, butterflies, fish, and some amphibians display this chromosomal sex determination system
ZZ-ZW
Bees, wasps, and ants belong to this Chromosomal sex determining system
Haplodiploidy system
in the Haplodiploidy system, males express this set while the females the other
Male-haploid set
Female- Diploid set
Found in some plants, fungi, protozoans, and fish; this system only has the sex-determining genes but no sex chromosomes
Genic Sex-determining system
Pseudoautosomal regions are regions where pairing occurs during meiosis, located?
at both tips of X and Y chromosomes- the short arm and the long arm
important in the MALE
the secondary pseudoautosomal region is located where on the chromosome?
the tip of the LONG arm
the primary pseudoautosomal region of the chromosome is located where?
the tip of the SHORT arm
ZW sex determination occurs in this gender?
the female
in Haplodiploidy, the males develop from?
UNFERTILIZED eggs and sperm are produced by MITOSIS. Somatic cells have a SINGLE set of chromosomes
in haplodiploidy, the females develop?
FERTILIZED eggs and somatic cells have TWO sets of chromosomes
Genes at one or more loci determine the sex of the individual is a concept of? found in?
Genetic Sex-determining systems
plants and protozoans
Sequential hermaphroditism is an example of the “common slipper limpet” in this sex-determining system?
Environmental- where the males transform into females and mate with other males.
heterogametic sex in the XX-XO system is characteristic of which sex?
the male
Drosophila have how many chromosomes?
three pairs of autosomes and one pair of sex chromosomes
total of 8
does the presence of a Y chromosome determine maleness?
no. example, the Drosophila. each fly’s sex is determined by balance between genes on autosomes and genes on the X chromosome in a Genic Balance System.
* X-female
* Autosome-Male
XXX is expressed as this sexual phenotype
Metafemale
XXY is expressed as this phenotype
female
XXXY is expressed as this sexual phenotype
metafemale
three sets of haploid chromosomes with a sex chromosome complement of XX is expressed as this sexual phenotype
intersex
three sets of haploid chromosomes with its sex chromosome complement XO is expressed as this sexual phenotype
Metamale
three sets of haploid chromosomes with its sex chromosome complement XXXX is expressed as this sexual phenotype
metafemale
what is the Sex determining region of the Y chromosome that causes neutral gonads to develop into testes?
sry gene
sry gene encodes a protein that binds to this complex molecule to cause a sharp bend in the molecule
DNA
the sry gene is located in this region of the chromosome?
the short arm
the androgen receptor is encoded by a gene on which chromosome?
the X chromosome
low hairline, broad chest, folds on neck, females with undeveloped sex characteristics, usually infertile, and a sex pair chromosome of XO in humans. this type of Androgen-sensitivity syndrome is known as?
Turner Syndrome
This syndrome usually affects males that have aneuploidy in their sex chromosomes. XXY, XXXY, XXYY. They present with small testes, reduced facial and pubic hair, and often taller than normal.
Klinefelter Syndrome
the concept that the Barr body is an inactive X chromosome
Dosage Compensation
the number of Barr bodies correlate with the number of X chromosomes - 1. X-1=#of Barr bodies.
XXXY will have how many Barr bodies based on the above info?
2
X inactivation is brought about by the action of this? an RNA molecule
Xist- X inactivation specific transcript
Xist RNA modifies Histones how?
methylation, deacetylation, and alteration of histone composition.
which region escapes X inactivation?
pseudoautosomal region
X inactivation takes place in humans during the 3rd month of development. T/F?
false, occurs during the first few weeks
mutated CFTR causes chloride channels to remain closed which results in thick, sticky mucous on the apical surface of respiratory epithelial cells. This genetic disorder is known as? and which chromosome defect does it occur on?
Cystic Fibrosis. the long arm of Chromsome 7
at the Phenotypic level, heterozygotes produce both normal and mutated CFTR at the cellular level. These people would be Carriers of the gene. This is an example of?
Co-dominance
if the phenotype of the heterozygote falls between (red, hot pink, pale pink, white) the phenotype range (red or white) of the two homozygotes, dominance is said to be?
Incomplete.
Phenotypes of the Heterozygotes includes the phenotypes of both homozygotes
Codominance
phenotype of the heterozygote is the same as the phenotype of ONE of the homozygotes.
Complete dominance
the percentage of individuals having a specific genotype that express the expected phenotype
Penetrance
the degree to which a character is expressed
Expressivity
Human polydactyly exhibits?
incomplete penetrance and variable expressivity
type O blood are the?
universal donors
Type AB blood are the?
universal recipients
B type blood produce which antigen and antibody type?
Antigen- B
Antibody-A
if your body produces Anti A and Anti B, which blood type do you have?
Type O ii
a person with type A blood received blood with A antibodies. will anything happen?
yes, the person received type B blood and the person is not compatible with the donation. the blood will clump together.
the masking of one gene by another gene at a different locus is called?
Epistasis
the gene that is masked is called the?
Hypostatic gene
the gene that does the masking is called the?
Epistatic gene
recessive epistasis refers to the presence of?
either two homozygous recessive genotypes that will mask the hypostatic gene.
homozygous dominant or heterozygous genotypes that mask the effects of the hypostatic gene is called?
Dominant epistasis.
how does the Bombay phenotype help explain epistasis?
people with the Bombay phenotype are homozygous for a recessive (h) mutation that fails to convert the intermediate into dominant (H). Type O blood can result from the masking of a terminal sugar on compound H or from the absence of compound H itself. Genotypes at both the H locus and the ABO locus determine the ABO blood type.
a duplicate recessive epistasis with a 9:7 ratio results in snails expressing?
Albinism
a ratio of 12:3:1 yields this type of interaction?
dominant epistasis.
recessive epistasis gives this ratio
9:3:4
a typical phenotypic ratio of 9:3:3:1 gives this type of interaction
no interaction takes place.
when does Complementation occur?
if an individual organism possessing two recessive mutations has a wild-type phenotype
ex:eye color in Drosophila
Sex-influence characters are determined by?
autosomal genes according to Mendelian principles. expressed differently in males and females
Sex-limited characters are determined by?
autosomal genes, expressed in only one sex, and have zero penetrance in the opposite sex
ex: cock-feathered males vs hen-feathered males.
Cock-feathering is an Autosomal dominant or recessive trait?
recessive
characteristics of these traits present in males and females, usually inherited from the maternal parent, exhibit extensive phenotypic variation, and the reciprocal crosses yield different results
Cytoplasmically inherited traits.
ex: stem and leaf color in the four’o clock plant
the genotype of the mother determines the phenotype of the offspring but not its own.
Genetic Maternal effect
Prader-Willi and Angelman syndrome are examples of this differential expression
Genomic Imprinting
this mutation deletion in the long arm of Chromosome 15 is inherited from the Father
Prader-Willi Syndrome
this mutation deletion is in the long arm of Chromosome 15 inherited from the Mother
Angelman Syndrome
in Mammals, methylation is erased in Germ cells of each generation and then reestablished in the course of?
gamete formation
sperm and eggs undergo different levels of ____, resulting in the differential expression of male and female alleles in the offspring.
methylation
human lgf2 locus is located on the?
short arm of Chromosome 11
Characteristics with only a few easily distinguishable phenotypes defines this term. “Qualitative”
Discontinuous Characteristics.
ex: tall vs short, red vs white
Characteristics by a continuous distribution of phenotypes. “Quantitative” often polygenic and or multifactorial
Continuous Characteristics
ex: human weight, human height, milk production in cattle, and Blood pressure in humans.
define polygenic characteristics
characteristics encoded by gene at multiple loci
ex:kernel color in wheat
characteristics that are polygenic and also influenced by environmental factors is? an example is Human intelligence
Multifactorial
Pleiotrophy is?
when one gene affects multiple characteristics
ex: recessive allele for phenylketonuria
Fragile X syndrome and Huntington disease are examples of?
Anticipation- related to expanding nucleotide sequences
