MIDTERM LECTURE Flashcards
Studied inheritance of traits using pea plants
Develop the laws of inheritance
Between 1856-1863, Mendel experimented
28,000 pea plants.
He found that plants’ offspring retained traits of the parents.
Gregor Mendel
Mendel stated that physical traits are inherited
as
Particles
two forms of a gene (dominant &
recessive)
Alleles
stronger of two genes expressed in
the hybrid; represented by a capital letter (R)
Dominant
gene that shows up less often in a
cross; represented by a lowercase letter
Recessive
- gene combination for a trait
Genotype
- the physical feature resulting from
a genotype.
Phenotype
gene combination involving 2 dominant or 2 recessive genes
Homozygous genotype
- gene combination of one dominant & one recessive allele (e.g. Rr); also called hybrid
Heterozygous genotype
what are the eight pea plant traits
seed shape, seed color, seed texture, pod shape, pod color, flower color, flower position, stem length
the parental generation in a breeding experiment
Parental P1 Generation
the first-generation offspring
in a breeding experiment
F1 generation
the second-generation offspring in a breeding experiment
F2 Generation
cross involving a single trait
Monohybrid cross
cross involving two traits. eg. flower color & plant height
Dihybrid cross
In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next
Law of Dominance
During the formation of gametes (eggs or
sperm), the two alleles responsible for a trait
separate from each other.
Alleles for a trait are then “recombined” at
fertilization, producing the genotype for the
traits of the offspring
Law of Segregation
Alleles for different traits are distributed to
sex cells (& offspring) independently of one
another.
This law can be illustrated using dihybrid
crosses
Law of Independent Assortment
A breeding experiment that tracks the
inheritance of two traits
Dihybrid cross
punnett square has 64 boxes… demonstrating that Mendel’s principles apply to the inheritance of multiple traits
The basic concepts are the same as with mono-or dihybrid crosses
each gamete must have ONECOPYOFEACHGENE
random segregation and independent
assortment still apply
Trihybrid Cross
Breaks down multi-hybrid crosses into a series of monohybrid crosses
Combine the individual ratios (multiply)to get the final ratio.
Can find genotypic ratios
Forked-line Method
contain the genetic material that is transmitted from parent to offspring and from cell to cell.
Chromosome
one of the two members of each pair segregates into one daughter nucleus, and the homolog segregates into the other daughter nucleus. Gametes contain one set of chromosomes—they are haploid.
Meiosis
- determining the type of inheritance pattern that a gene follows.
– provide important clues concerning the pattern of inheritance of traits within human families.
Pedigree Analysis
________ is at the top of the
pedigree and the most recent generation is at ________.
Oldest, Bottom
In humans, disorders or traits caused by a single gene are called
Mendelian traits
Is the Likelihood That an Out come Will Occur
Probability
number of times an outcome will occur/ total number of possible outcomes
Probability
The deviation between the observed and expected outcomes is called
Random Sampling Error
states that the probability that two or more independent events will occur together is the product of their individual probabilities
Multiplication rule
states that the probability that
any one of two or more mutually exclusive
events will occur is calculated by adding
together their individual probabilities
Addition Rule
equation represents all of the possibilities for a given set of two unordered events.
Binomial Expansion Equation
Used to Test the Validity of a Genetic Hypothesis
Chi-square test
when it assumes there is no real difference between the observed and expected values.
Null hypothesis
one that the experimenter has failed to realize, may also be consistent with the data
Alternative hypothesis
The Cross: A true-breeding fly with straight wings and a gray body (c+c+e+e+) is a cross to a true-breeding fly with curved wings and an ebony body(ccee). The flies of the F1 generation are then allowed to mate with each other to produce an F2 generation
The Outcome:
F1 generation: All offspring have straight wings and gray bodies
F2 generation: 193 straight wings, graybodies 69 straight wings, ebony bodies 64 curved wings, gray bodies 26 curved wings, ebony bodies
Total: 352
With df = 3, the chi square value of 1.06 we obtained is slightly greater than1.005, which gives a P value of 0.80, or 80%.
To reject the null hypothesis at the5%significance level, the chi square would have to be greater than 7.815. Because it is actually far less than this value, we accept that the hypothesis is correct
Two pea plants are heterozygous for three genes (Tt Rr Yy), where T = tall, t = dwarf, R= round seeds, r= wrinkled seeds, Y =yellow seeds, and y = green seeds. If these plants are crossed with each other, what
are the predicted phenotypes of the offspring, and what fraction of the offspring will occur in each category?
Pakisagot
refers to inheritance
patterns that obey two laws:
A. The law of Segregation
B. Law of Independent Assortment
Mendelian Inheritance
observed ratios in the offspring clearly obey Mendel’s laws.
Simple Mendelian Inheritance
This pattern involves the inheritance of genes that are located on the X-chromosome. In mammals and fruit flies, males have a single copy of X-linked genes, whereas females have two copies
X-linked
This pattern refers to the effect of sex on the individual’s phenotype. Some alleles are recessive in one sex and dominant in the opposite sex.
Sex-influenced Inheritance
In this pattern, a trait occurs in only one of the two sexes. An example is breast development in mammals.
Sex-limited inheritance
prevalent alleles in a natural population.
Wild type
phenomenon in large population when more than one wildtype allele occur.
Genetic Polymorphism
altered pre-existing alleles cause by random mutation that occurs in the population
Mutant Alleles
mutant alleles aren’t often defective in their ability to express a functional protein. TRUE OR FALSE?
FALSE
- change the gene or the protein encoded by a gene so that it gains a new or abnormal function.
Gain-of-function mutations
change a protein such that the mutant protein acts antagonistically to the normal protein.
Dominant-negative mutations
- dominant mutant allele is a loss of-function allele.
Haploinsufficiency
used to describe patterns of inheritance in which a heterozygote (with one functional allele and one inactive allele) exhibits an abnormal or disease phenotype
Haploinsufficiency
is a situation in which an allele that
is expected to cause a particular phenotype does not.
incomplete penetrance
degree to which trait is expressed.
Expressivity
refers to the effects of
environmental variation on a phenotype
norm of reaction
condition in which the phenotype of a
heterozygote is intermediate between the
corresponding homozygous individuals.
Incomplete Dominance
is the interaction between genes that are alleles and result in the heterozygous individuals being superior to either of the homozygous parents.
Overdominance
occurs when both alleles are expressed equally in the phenotype of the heterozygote.
Codominance
A black chicken and a white chicken are crossed. Show the punnet square. What is the probability that they will have erminette chicks?
100%
may exist in a population level, and different individuals in the population may have different pairs of these alleles.
Multiple Alleles
displays both co-dominance and complete dominance.
Blood type
can either have a carbohydrate on their surface or not.
Red Blood Cells
If a woman with AB blood has children with a man who has type O, what will be the possible genotypes of their children? What will be their blood type?
PAKISAGOT
Genes for some traits are found on the
Chromosomes
They do not show the trait, but carry a gene for
the trait
Carriers
If a woman with normal vision has children with a man who is colorblind, what are the chances that their children will be colorblind? Will any children be carriers of the trait?
ANSWER PLEASE
If an allele makes one of these genes
nonfunctional, or causes it to take on an
abnormal, harmful activity, it may be
impossible to get a living organism with a
homozygous genotype.
Lethal Genes
occurs when the expression of a single gene has two or more phenotypic effects
Pleiotropy
The multiple effects of a single gene on the phenotype of an organism is called
Pleiotropy
Phenomenon that describes how
the allelic variants of two different genes affect a single trait.
can exhibit epistasis and complementation.
Gene Interactions
the interaction between genes is antagonistic, such that one gene masks or interferes with the expression of another.
The alleles that are being masked or silenced are said to be hypostatic to the epistatic alleles that are doing the masking.
The expression of one gene is dependent on the function of a gene that precedes or follows it in the pathway.
Epistasis
It is a simple or dominant
epistasis whenever a dominant allele conceals the expression of both recessive and dominant alleles at other loci.
Dominant Epistasis
What are 5 types of Epistasis
Dominant, Recessive, Dominant Inhibitory, Duplicate Recessive, Duplicate Dominant
when the recessive allele conceals the expressing.
Recessive Epistasis
when genes conceal other
genes by suppression
Dominant Inhibitory
There is a recessive allele concealing the expression of dominant alleles at two loci
Duplicate Recessive
there is a dominant allele concealing the expression of recessive alleles at two loci.
Duplicate Dominant
In human families it is often observed that certain characteristics may “skip” a generation,
then reappear. How would you explain this in the light of the facts expounded by Mendel?
ANSWER
In Holstein cattle the spotting of the coat is due to a recessive gene while a solid–coloured
coat is dominant. What types of offspring might be produced by a cross between two
spotted animals? Show how you reach your conclusion. The gene P is responsible for coat
pattern.
PAKISAGOT
In cats the gene for short hair is dominant over the gene for long hair (angora). A short–
haired tom is mated with an Angora female. She bears eight kittens, six short–haired and
two with long hair. How do these numbers compare with the expected ratio? If you mated
these same cats four more times and obtained a total of forty offspring, would you expect
the results to be a closed approximation of the expected ratios? Explain.
Walang titingin sa sagot
The hornless condition in cattle is dominant over horned. A cattleman has a herd of
hornless cattle only, but some horned cattle occasionally appear. These are removed from
the range before they can reproduce. Assuming that this man has good fences which can
keep out stray bulls, how could this be explained?
ANSWER
In summer squash, white coloured fruit is dominant over yellow. If you place pollen from a yellow–fruited plant on the pistil of a hybrid white–fruited ( heterozygous ) plant, what type of seeds would you expect from the seed which come from this cross?
SAGOT
An albino man marries a normally–pigmented woman who had an albino mother. Show the
types of children that this couple may have and the proportions of each. ( Albino is
recessive; normal is dominant ).
Walang mandadaya
In Drosophila, vestigial wings and ebony colour are due to two separate recessive genes.
The dominant alleles are normal (long) wings and normal (gray) body colour. What type of
offspring would you expect from a cross between a bomozygous vestigial ebony female and a normal double homozygous (long–winged, gray–bodied) male? If the F1 are allowed to breed among themselves what types of offspring would you expect in the F2? Show complete genotype and phenotype of both generations.
Practice to
About 70% of Americans get a bitter taste from a chemical called phenyl thiocarbamide
(PTC); the others do not. The ability to taste this chemical results from a dominant gene
while taste–blindness is recessive. A normally pigmented woman who is non–taster has a
father who is an albino–taster. She marries an albino man who is a taster, but who has a
mother who is non–taster. Show the types of children which this couple may have.
SAGOT
In mice, the gene C for coloured fur is dominant over its allele c for white. The gene V
for normal behaviour is dominant over v that for waltzing. Give the probable genotypes of
the parent mice (each was mated repeatedly) that produced the following offspring:
a. coloured–normal mated with white–normal, produced 29 coloured–normal and 10
coloured–waltzers;
b. coloured–normal mated with coloured–normal, produced 38 coloured–normal, 15
coloured–waltzers, 11 white–normal and 4 white–waltzers;
c. coloured–normal mated with white–waltzer , produced 8 coloured–normal, 7 coloured–
waltzers, 9 white–normal and 6 white–waltzers.
ANSWER
A colour blind man marries a woman with normal vision. Her mother was colour blind.
What kind of children would you expect from this marriage?
SAGOT
Suppose a young lady comes to you for advice in your capacity as a marriage counselor.
She tells you her brother has hemophilia, but both of her parents are normal. She wishes
to marry a man who has no history of hemophilia in his family. She would like to know
the probability of having hemophilic offspring. Explain.
EXPLAIN
Two drosophila are crossed and yield 82 females and 38 males. Such a great deviation
from the expected 1:1 ratio could hardly be due to chance. Suggest an alternate
explanation. Think on this one.
ANSWER
A woman bears a child with erythroblastosis at her second delivery. She has never had a
blood transfusion. On the basis of this data, classify the woman, her husband and both
children as to Rh type.
WHY
A woman is Rh positive and both of her parents are Rh positive. She marries an Rh
negative man. Is there any chance that they may have any Rh negative children? Explain.
PAKISAGOT
Can a child having blood type A be born to parents having types AB and B respectively?
Explain.
PAKISAGOT
- study of Heredity and Variation of
Inherited Characters - science of genes, heredity, and
variation in living organisms - Study of the way animals and
plants pass traits on their offspring - study of how traits are passed from
parent to offspring
Genetics
The tendency offspring to resembles their parents
Heredity
The tendency of offspring to vary from their
parents.
Variation
segment of DNA
that determines a trait.
Gene
Who coined the word “gene”?
Wilhelm Johannsen
What are the branches of Genetics
- Classical Genetics
- Molecular Genetics
- Population Genetics
- Quantitative Genetics
- Transmission of traits form
generation to generation. - Governed by Mendel’s Laws
- Study of physical traits as a
stand-in or the gene that
control appearance, or
phenotype
Classical Genetics
- Chemistry of Genes
- Investigate the structure
and functions of genes at
molecular level - Investigate the physical
and chemical structure
DNA - Genetic code
Molecular Genetics
- Use of mendelian genetics
to examine inheritance
patterns of individuals in a
population. - understand how the
collective genetic diversity of
a population influences the
health of individuals within
the population.
Population Genetics
- Measuring the strength of heredity.
- examines traits that vary in really
subtle ways - relate those traits to the underlying
genetics of organisms. - estimate how much variation in a
particular trait is due to the
environment and how much is
actually genetic.
Quantitative Genetics
Application of Genetics
- Forensics
- Common ancestry
- Prediction of Disease
- Development of treatments
- Family Planning/Genetic Counseling
- Agriculture
- Biotechnology
- Crop and Animal Breeding
- Genetically Modified Organisms
- Ecology
✓ small, membrane-enclosed units
✓ Filled with aqueous solution of chemicals
✓ Ability to multiply or divide
✓ Fundamental unit of life
Cell
Who proposed cell theory?
Matthias Schleiden and Theodore Schwann
who said that all cells arise from pre-existing cell
Rudolf Virchow
in a nucleoid or nucleus
genetic material
a semifluid matrix
cytoplasm
a phospholipid bilayer
plasma membrane
are required to visualize
cells.
microscope
can resolve structures that are 200nm apart.
Light microscope
can resolve structures that are 0.2nm apart.
Electron microscope
two basic types of cells
Prokaryotic cell and eukaryotic cell
- Region of cytoplasm where
prokaryote’s genome/ DNA
is located. - Usually a singular, circular
chromosome.
Nucleoid
- Small extra piece of
chromosome/genetic material. - 5 - 100 genes
Plasmid
- Also known as proto-plasm.
- Gel-like matrix of water,
enzymes, nutrients, wastes, and
gases and
contains cell structures. - Location of growth,
metabolism, and replication.
Cytoplasm
- Bacteria’s way of storing
nutrients. - Staining of some granules aids
in identification.
Granules
✓is thought to be a
feature only of eukaryotes.
✓ is a major advancement in the
study of prokaryotes.
Cytoskeleton
✓Separates the cell
from its environment.
✓Phospholipid bilayer
✓hydrophilic – water
loving
✓hydrophobic –water
fearing
✓Membrane is semi-
permeable.
Plasma membrane
Long, thin extensions
Flagella
Wind around bacteria,
causing movement in waves.
Axial filament
short, fine
appendages around the cell.
✓No role in motility
Fimbriae
tubes that are longer
than fimbriae but shorter than
flagella.
Pili
- are not made of cells
- need a host cell to reproduce
- very small compared to a cell.
- Like cells, viruses contain nucleic acids
Virus
✓has a nucleus
✓can be single or multicellular
✓have many organelles, performing
complex functions
✓specialized to perform specific functions
✓larger than prokaryotic cells
✓Animals, plants, fungi and protists are
made of eukaryotic cells
Eukaryotes
- Nickname: “The
Control Center” - Function: holds the
DNA
Nucleus
Consists of:
✓Cytosol – liquid portion
✓Organelles – specialized
cellular compartments
✓Inclusions – chemical
substances
✓Glycogen (muscle & liver
cells)
✓Lipid droplets (fat cells)
✓Melanin granules (skin & hair
cells)
Cytoplasm
Nickname:
“The Powerhouse”
✓Function: Energy formation
✓Breaks down food to make
ATP
✓ATP: is the major fuel for all cell
activities that require energy
Mitochondria
- Function: makes
proteins - Found in all cells,
prokaryotic and
eukaryotic - dense particles
of rRNA and
protein
Ribosomes
synthesize proteins that
function within the cell
Free ribosomes
synthesize proteins
incorporated into cell membranes
Attached ribosomes
thick rods
composed of tubulin.
Microtubules
thin filaments composed of
actin
Microfilaments
tough protein fibers
Intermediate filaments
fingerlike
projections of the plasma
membrane;
✓increase surface area for
absorption
Microvilli
short hair-like
projections;
✓propel substances over
surface of cell
Cilia
long hair-like
projections; propel the cell
Flagella
Nickname: “Roads”
Function: The internal delivery system of the cell
Endoplasmic Reticulum
Nickname: The shippers
Function: packages, modifies, and
transports materials to different
location inside/outside of the cell
Appearance: stack of pancakes
Golgi Apparatus
circular (but bigger than ribosomes)
✓ Nickname: “Clean-up Crews”
✓Function: to break down food into particles the rest of
the cell can use and to destroy old cells.
Lysosomes
✓ membranous sacs of oxidase & catalase
enzymes;
✓ detoxify alcohol & neutralize dangerous
free radicals.
Peroxisomes
✓Have a cell wall and cell membranes
✓Have a large vacuole unlike the animal cell
which only has small vacuoles
✓Have mitochondria to convert sugar to usable
energy for the cell
✓Have a few lysosomes
✓Are more rectangular in shape
✓Have chloroplasts to carry out photosynthesis
✓Make sugar to store solar energy
Plant Cells
✓Function: stores water
✓This is what makes lettuce crisp
✓When there is no water, the plant wilts
Vacuoles
✓Function: traps energy from the sun to produce food for the plant cell
✓Green in color because of chlorophyll, which is a green pigment
Chloroplast
✓Function: provides
support and
protection to the
cell membrane
✓Found outside the
cell membrane in
plant cells
Cell wall
✓Can not make their own food
✓Have many lysosomes
✓Are more round shaped
✓Have centrioles
✓Use mitochondria to release energy
✓Have many Golgi bodies
✓Have more extensive cytoskeleton than plant
cells
Animal cells
- The Cell grows,
- Organelles Double
- Nucleus splitting
Interphase
is when organelles double.
Remember each new cell needs a complete set of organelles.
G1
when DNA is replicated.
Each cell needs a complete and identical set of DNA
S
Proteins needed for Mitosis are produced.
G2
- chromosomes condense
- spindle fibers form (spindle fibers
are specialized microtubules - radiating out from centrioles)
- chromosomes are
captured by spindle
- chromosomes are
Prophase
- chromosomes align along
equator of the cell, with one
kinetochore facing each pole.
Metaphase
- sister chromatids separate
- spindle fibers attached to
kinetochores shorten and
pull chromatids towards the
poles. - free spindle fibers lengthen
and push poles of cell apart
Anaphase
- spindle fibers disintegrate
- nuclear envelopes form around both groups of chromosomes
*chromosomes revert to their extended state - cytokinesis occurs, enclosing each daughter nucleus into a separate
cell
Telophase
undergo
cytokinesis through the
formation of a cleavage
furrow.
Animal cells
A ring of microtubules
contract, pinching the cell
in half.
Cytokinesis
undergo cytokinesis
by forming a cell plate between
the two daughter nuclei.
Plant cells
2 types of body cells
somatic cells and sex cells
A single germ cell divides into four unique daughter cells.
- Daughter cells have half the # of chromosomes as parent cell,
so they considered haploid.
Meiosis
Refers to the number of sets of
chromosomes in cells.
Ploidy
one copy of each chromosome
– designated as “n”, the number of
chromosomes in one “set”
- gametes
Haploid
two sets of chromosomes
- two of each chromosome
– designated as “2n”
- somatic cells
Diploid
Are paired chromosomes with genes for the same
trait arranged in the same order.
Homologous chromosomes
Stages of Prophase
Leptotene, zygotene, pachytene, diplotene, diakinesis
all maternally and paternally derived chromosomes have
found their homologous partner.
* The homologous pairs then undergo synapsis, a process by which
the synaptonemal complex (a proteinaceous structure) aligns
corresponding regions of genetic information on maternally and
paternally derived non-sister chromatids of homologous
chromosome pairs.
Zygotene
stage where genetic exchange between the non-sister
chromatids of the synaptonemal complex happens in an event known
as crossing-over or genetic recombination.
Pachytene
crossing over is completed homologous
chromosomes retain a full set of genetic information; however,
the homologous chromosomes are now of mixed maternal and paternal
descent. Visible junctions called chiasmata hold the homologous
chromosomes together..
Diplotene
