Midterm 1 Flashcards
genetics is the branch of biology that deals with
heredity and variation
genetics is used to analyze genes –
in vivo
two plant breeders who paved the way for Mendel’s experiments
Thomas Knight and John Goss
peas were good because
short generation time, numerous varieties available, ability to cross fertilize and self-fertilize
Goss established: peas were a good genetic system with clear –
heritable traits
Goss established: parental characteristics could disappear for a generation and then reappear which could only be explained if units of heredity were – in nature
particulate
Mendel brought methods that were – to biology
standard in Physics
Mendel’s contributions
limited the number of variables
quantitated resulta
model that can be tested
visible characteristics
phenotype
Mendel’s hybrids had - in F1
uniformity
Mendel’s hybrids tended to – in F2
revert to parental phenotypes
Mendel’s theory: heredity determinants are of a – nature
particulate
Mendel’s theory: each adult pea has – determinants for each character
2
Mendel’s theory: the – only have 1 determinant for each character
gametes
Mendel’s theory: each determinant – into gametes
segregates equally
Mendel’s theory: union of 2 gametes occurs – with regard to genetic determinants
randomly
since egg and sperm were believed to contribute equally to offspring, – probably contained genetic material
chromosomes
eukaryotic cells contained – which contained chromosomes
nuclei
haploid
only one set of chromosomes, one copy of each gene
all chromosomes come in pairs (except sex chromosomes)
diploid organisms
diploid organisms - each homolog has the same number and order of genes though may have different –
alleles
impossible to tell – from chromosome pairs
genome size
each chromatid is
one DNA molecule
an organized profile of an organism’s chromosome
karyotype
chromosomes are made up of
DNA and protein (chromatin)
DNA is packaged into –
nucleosomes
chromatin in M phase is –
always condensed
heterochromatin
condensed state of interphase chromatin
heterochromatin is rich in repeated sequences, transposable elements, and –
centromeric DNA
chromosomes duplicate during
S phase
chromosomes segregate during
M phase
replicated chromosomes remain connected at –
centromere
each chromosomes is – before replication
one DNA molecule
spindle fibers attach to protein complexes called – that assemble on the centromere
kinetochores
centromeres can vary in position
metacentric/acrocentric
nuclear division associated with somatic cell division
mitosis
mitotic cell division results in
2 identical daughter cells
c = concentration of DNA relative to gamete or –
of chromatids per chromosome pair
n = # of –
chromosomes in gamete
describes how DNA is segregated into gametes
meiosis
reductional division
meiosis I
meiosis I
homologous chromosomes separate
equational division
meiosis II
meiosis II – separate
sister chromatids
gametes have – alleles
one
law of segregation (1st law)
two alleles of a gene separate during gamete formation and end up in different gametes
changes in DNA sequence
mutants
in humans, presence of – determines maleness
Y chromosomes (SRY gene)
– is the default sex
female
SRY transcription factor activates gene responsible for –
testis development
genes on sex chromosomes – involved in sex functions
are not necessarily
disease related on X chromosome is much more likely to be seen in
males
X-linked dominant traits would be observed more in males or females?
females
T/F: Y chromosome evolved from X chromosome
true
genes are named after
first mutant allele
a
recessive allele
a+
wild type allele dominant to mutant
A
dominant allele
A+
wild type allele recessive to mutant
1902: Sutton and Boveri :Chromosome Theory of Inheritance
genes are located on chromosomes
points against chromosome theory of inheritance :chromosomes disappear in –
interphase (break apart?)
points against chromosome theory of inheritance: cytologically difficult to prove homologs pair in meiosis
could be random pairing
points against chromosome theory of inheritance: if genes are linked on chromosomes assortment of genes should –
not be independent
in flies, sex is determined by –
of X chromosomes
phenotype is expressed only in one sex
sex-limited trait
in sex limited traits, – possess genes, but only expressed in one sex
both sexes
sex determines whether an allele is dominant or recessive
sex influenced trait
sex influenced trait may affect the extent of –
expression
pattern baldness is an example of
sex influenced trait
humans: one of the X’s is – early in development in females
inactivated
human females randomly inactivates one of the X’s are –
mosaics
down syndrome correlates with nondisjunction in mother
meiosis I (50% no crossing over)
meiosis arrested in – for decades
prophase I
1st law: for each gene, a gamete will end up with either allele from -
the mother of the allele from the father
always assume wild type is
homozygous
proof of the chromosomes theory of inheritance came from what research
study of sex-linked genes in Drosophila
Why do we have 1:1:1:1: phenotypic ratio in the F2?
because F1 females are heterozygous and because the F1 males behave like a tester strain
in flies sex is determined by –
number of X chromosomes
T/F: most traits are affected by more than one gene and cannot be analyzed using simple Mendelian genetics
true
recessive traits appear in progeny of –
unaffected individuals
recessive traits frequently show up in – matings (cousins)
consanguineous
for recessive traits: – from two affected individuals are affected
all progeny
probability of independent event occurring together is the – of the probabilities of the individual events
product
probability of either of two mutually exclusively event occurring is the – of their individual probabilities
sum
affected individuals appear in every generation
dominant traits
for dominant traits: two affected parents may have –
unaffected progeny
mendelian ratios apply to – genes (3:1 or 1:1)
autosomal
sex-linked genes obey Mendel’s laws but do not –
give Mendelian ratios
each dihybrid plant produces 4 gamete types –
with equal frequency
Mendel’s Second Law
segregation of alleles of two different genes are independent of one another
law of independent assortment is explained by genes being located on –
different chromosomes
In the first division of meiosis, alleles are segregated
Mendel’s first law
the first division of meiosis also segregates chromosomes independently
Mendel’s second law
one gene (two phenotypes)
3: 1 F2 phenotypic ratio
1: 1 test cross phenotypic ratio
two genes (four phenotypes)
9: 3:3:1 F2 phenotypic ratio
1: 1:1:1 test cross phenotypic ratio
null hypothesis
A and B are unlinked expect a 9:3:3:1 F2 phenotypic ratio or 1:1:1:1 test cross phenotypic ratio
degrees of freedom =
of independently variable classes
if p
reject null (reject independent assortment with differences by chance alone)
single trait determined by multiple genes
polygenic inheritance
hardening of the arteries
athersclerosis
both mitochondria and chloroplast contain – though they rely on nuclear genes as well
small circular chromosomes
each cell contains many copies of the organelle, and each organelle contains many copies of the –
chromosome
cytoplasmic organelles are inherited through the –
mother
– during prophase I leads to crossover gametes
chiasma
crossing over: homologous recombination that is catalyzed by a set of –
enzymes
1% recombination =
1 map unit
frequency of recombination is proportional to the genetic – (based on the assumption that recombination is random)
distance
examine linkage of autosomal genes? for simplification, instead of crossing F1 progeny (where recombination could occur in either parent), F1 females are crossed to –
tester male
recombination frequency often differs between
males and females
drosophila is an extreme where there is no recombination in –
males
we can never measure more than – between two genes even if they are further away than –
50 mu
genes on different chromosomes also give – mu
50
two genes located on different chromosomes give – recombinants
50%
if genes are on the – some meiosis will have no recombination between genes
same chromosome
if all meiosis have one or two recombination events between A and B, then the map distance will equal to 50 and A and B are considered –
unlinked
genes located far away on same chromosome will have 50% recombinant gametes and appear
unlinked
if some meiosis do not have a recombination between A and B, then there will be more parentals than recombinants and A and B are said to be
linked
each gene has a place or – on its chromosome
locus
mutation – a gene and locus
marks
genes or segregating allele are called
markers
2 genes are linked
on the same chromosome
– linkage group per chromosome pair
one
groups of linked genes are known as –
linkage groups
when similar alleles are on the same chromosome
cis
when alleles are on different chromosomes
trans
w+y+/wy
cis
w+y/wy+
trans
when markers are relatively far apart, the observed distance is usually – than the sum of distances due to double crossovers
less
wild type alleles usually encode the – functional protein
normal
mutant allele changes either –, splicing, or amino acid sequence of protein
expression
T/F: phenylketonuria is one of the most common genetic abnormalities in US
true
if one copy of the gene is sufficient for normal function, then most non-functional alleles are –
recessive
if one copy is not sufficient for normal function, the wild-type is said to be – and the mutant allele is dominant
haploinsufficient
mutant allele is recessive
haplosufficient
mutant allele is dominant
haploinsufficient
ABO blood types exhibit
co-dominance and complete dominance
I gene encodes enzyme that adds – to membrane proteins
sugars
i allele is
nonfunctional (no sugar)
F1 hybrids show the traits intermediate between two parents
incomplete dominance
phenotype usually reflects genotype
incomplete dominance
F1 hybrids show the traits of both parents
co-dominace
everything is – when you get down to the level of DNA (when you make both mutant and wild-type)
co-dominant
any allele found – frequency in the wild is considered “wild type” other alleles are “mutant”
> 1% (all bloods types are considered wild type)
3:1 or 1:2:1 ratio
1 gene with different alleles
2:1 ratio is usually
lethal allele
condition in which a single gene has more than one effect on an individual
pleiotropic effect
recessive - lethality (YY)
dominant - coat color (Yy) and sickle cell and malaria
pleiotrophic effect
in – organisms, mutations in essential genes are lethal
haploid
lethal under some conditions but can survive under other conditions
conditional mutants
most traits are the result of –
many biochemical step
production of wild-type phenotype when two recessive mutant alleles are brought together in the same cell
complementation analysis
different gene =
complement
two different alleles of same gene
do not complement
complementation of 2 genes with no intermediate phenotypes
9:7 ratio
”–” means they are in the – complementation group
same
gene that acts first is – (stands over) to the second gene
epistatic
mutations that reverse the effect of an original mutation resulting in wild-type phenotypes
suppressors
suppressors usually from – a mutant
mutagenizing
different ratios are observed if suppressor has mutant phenotype by itself; can be observed if the two proteins interact to form a –
complex
interacting proteins (suppressor)
10:6
biochemical pathway (suppressor)
13:3
two mutations have a stronger effect when combined
synthetic lethality (9:6 ratio)
15:1 ratio (everything is wild type except for double mutant)
duplicated genes
mutations which either increase or decrease the expression of a gene
modifiers
modifiers are frequently found in – proteins
regulatory
distinguish between multiple alleles and multiples genes by ratios of –
F2 phenotypes
1:1, 1:2:1 3:1
single gene, (might have) multiple alleles
1:1:1:1, 9:3:3:1 (or variation)
two genes, two alleles
need one good copy of each gene for expression of final phenotype
complementation (9:7)
recessive epistasis
9:3:4
dominant epistasis
12:3:1
– has unique life cycle which makes complementation analysis simple and distinct from recombination
neurospora (bread mold)
yeast have – haploid or diploid states
stable
2 cells combine: cytoplasm becomes one but their nuclei stay separate
heterokaryon
heterokaryon can’t have recombination but can have –
complementation
– immediately undergo meiosis
transient diploid
separate during anaphase II of meiosis
sister chromatids
contain identical nucleotide sequences prior to crossing over
sister chromatids
separate during anaphase of mitosis
sister chromatids
in a pair, one is of maternal origin, the other of paternal origin
homologous chromosomes
crossover between them contributes to genetic diversity
homologous chromosomes (nonsister chromatids)
separate during anaphase I of meiosis
homologous chromosomes
They all have some mutation in the same wing-development gene.
Each strain may have a –, but the same gene is mutated in all strains in a complementation group.
different mutation
To construct a mapping cross of linked genes, it is important that the genotypes of – of the gametes produced by the heterozygote can be deduced by examining the phenotypes of the progeny, taking into consideration that the homozygote produced only recessive gametes.
all
T/F: Gametes and their genotypes can never be observed directly
true
