Exam 1: Gen Bio Review Flashcards
Describe a chromosome, its anatomy, and its various forms
-A chromosome consisting of just one chromatid is a monad. If it has two chromatids, it is a dyad.
-A chromosome is made of chromatin fibers that coil and condense
-Chromosomes are visible only during mitosis and meiosis but are always present
-Electron microscopy of chromosomes in varying states of coiling led to the folded-fiber model
Compare and contrast the similarities and differences between homologous chromosomes and sister chromatids.
Homologous chromosomes: Homologous chromosomes contain identical gene sites along their length. Each site is called a locus. (2n) They pair up during meiosis.
Sister chromatids: The sister chromatids are joined to each other via the centromere and only become separated when cell division occurs. They are identical and are created through synthesis and separated during anaphase of mitosis and anaphase 2 of meiosis.
Contrast Complete, Incomplete, and Co- Dominance
Codominance: Joint expression of both alleles in a heterozygote
Complete Dominance: Dominant allele completely expressed.
Incomplete Dominance: Intermediate phenotype. This allelic relationship led to the incorrect concept of blending inheritance.
Gene
An inherited factor (encoded in the DNA) that helps determine a characteristic
Allele
One of two or more variations of a gene
Locus
Specific place on a chromosome occupied by an allele
Genotype
Set of alleles possessed by an individual organism
Phenotype or trait
An appearance of manifestation of a characteristic
Ex: Blue eyes
Characteristics or character
An attribute or feature
Ex: Eye color
Centrosome
An organelle near the nucleus of a cell which contains the centrioles from which the spindle fibers develop in cell division.
Centrioles
-They occur in pairs perpendicular to each other
-9 triplets of microtubule arrangements
-Nontubulin proteins hold them together
Nucleolus
An amorphous component of the nucleus where ribosomal RNA (rRNA) is synthesized and where the initial stages of ribosomal assembly occur
Nucleoid
The nucleoid is an irregularly shaped region that houses genetic material. This is only found in prokaryotes.
Diploid vs haploid
Haploid cells are those that have only a single set of chromosomes while diploid cells have two sets of chromosomes.
Centromere
The contricted region of the chromosome to which kinetochores form and microtubules attach.
Eukaryotic cell characteristics
-Polysaccharide cell walls
-Methionine
-Linear chromosomes, rarely plasmids
-80S Ribosomes
Draw metacentric, submetracentric, acrocentric, and telocentric chromosomes and be able to identify where the centromere is
1) Middle
2) Between middle and end
3) Close to end
4) End
What is the function of the telomeres?
They protect the ends of chromosomes
Pseudohomologues
Behave as homologs in meiosis
Ex: X and Y
Describe the characteristics of a model organism.
-easy to grow
-cheap
-observable characteristics with two distinct forms
-high brood size
-easy to selectively breed
-single season maturation time
-true-breeding strains
-precendence
-other research showed that pea hybrids could be produced
Describe the experimental details that contributed to Mendel’s success.
-good choice of a model organism
-simple experimental design
-good quantitative records
-seven visible features with two contrasting traits
Relate Mendel’s first three postulates to the results of a monohybrid cross.
1) Unit factors exist in pairs
2) Dominance/recessiveness of those pairs
3) Segregation of the alleles of a single gene
Relate Mendel’s forth postulate to the results of a dihybrid cross.
4) Independent assortment
Unit factors that determine different traits assort independently during gamete formation
All possible gamete combinations form with equal frequency.
Relate the rediscovery of Mendel’s work with the Chromosomal Theory of Inheritance.
-Genetic material in living organisms is contained in chromosomes
– Separation of chromosomes during meiosis served as basis for Mendel’s principles of segregation and independent assortment
Mendelian Genetics coupled with
Chromosomal Theory of Inheritance provides the basic principles of gene transmission
- Genes are present on homologous
chromosomes - Chromosomes segregate. Therefore the alleles of genes present on chromosomes segregate
- Chromosomes assort independently. Transmission of alleles at one gene locus does not
influence the transmission of other gene loci.
Describe the stages involved in mitosis
Prophase:
-Nuclear envelope breaks down
-Chromosomes condense and become visible
-Centrioles divide, move, establish poles
Prometaphase:
-Spindle fibers form
-Centrioles reach opposite poles
-Equatorial plane referred to as metaphase plate
-Period of chromosome movement to equatorial plane of cell
-Chromosomes are clearly double structures
Metaphase:
-Chromosome configuration following migration
-Centromeres align on metaphase plate
Anaphase:
-Sister chromatids separate into individual chromosomes and migrate to opposite poles
Telophase
-Cytokinesis
-Uncoiling of the chromosomes
-Re-formation of the nuclear envelope
– Spindle fibers disappear
– Nuclear envelope reforms
List the cell cycle checkpoints and describe what is being “checked” at each.
G1/S
-Monitors size cell has achieved
-Monitors condition
G2/M
-Monitors if DNA replication is complete
-Monitors damaged DNA
M (metaphase)
Monitors successful formation of spindle fiber system and attachment to kinetochores
List the major proteins involved in organizing and partitioning DNA throughout mitosis.
Kinetochore
-Multilayered protein plates associated with centromere
– Spindle fibers (microtubules) bind to kinetochore; chromosomes migrate
Cohesin:
-Protein complex that holds sister chromatids together
Shugoshin:
-Protein that protects cohesin from being degraded by separase at the centromere
Separase:
-Enzyme that degrades cohesin
Karyokinesis
Genetic material partitioned to
daughter cells during nuclear division
Interphase
G1
S: DNA is synthesized
G2
G0: Point in G1 phase where cells are
nondividing, but a metabolically active state
Nucleosome
The individual, beadlike histone DNA complexes that make up the subunits of chromatin
Differentiate between the terms dyad and diploid.
A chromosome consisting of just one chromatid is a monad. If it has two chromatids, it is a dyad.
Haploid cells are those that have only a single set of chromosomes while diploid cells have two sets of chromosomes
Describe the aspects of meiosis that contribute to genetic variation in sexually reproducing
species.
Crossing over, independent assortment, and segregation
Describe the Chromosomal Theory of Inheritance.
Genes are found on chromosomes
Explain the relationship between meiosis and Mendel’s principles of inheritance.
Mendel’s principle of segregation can be explained by the homologous pairing and segregation of chromosomes during meiosis
Mendel’s principle of independent assortment can be explained by the relative behavior of (nonhomologous) chromosomes during meiosis
Truebreeding
A kind of breeding wherein the parents would produce offspring that would carry the same phenotype if mated to itself.
Describe sex-influenced and sex-limited traits
Sex-influenced: dominant for males, recessive for females
Sex-limited: only one organism expresses the phenotype
Gene linkage
Two gene loci in close proximity will tend to be inherited together
Incomplete penetrance
A trait may not be visible despite
having the determinant genotype
Imprinting
The influence an allele has over a trait may change.
Wild-type (wt) allele
Occurs most frequently in
nature and is usually, but not always, dominant
Loss-of-function mutations
Hypomorphic- partial loss
Null- complete loss
Tay Sachs Disease
autosomal recessive on the physiological level and codominant on the molecular level
Reasons for mitosis
Growth
Development (zygote)
Cell division
What is one way you could distinguish prophase from pro metaphase?
Spindle fiber attachment appears in pro metaphase
Dihybrid is synonymous with
heterozygous
Can a crossover cause a dyad chromosome to have non-identical sister chromatids?
Yes
Does the Chromosomal Theory of Inheritance state that DNA is the inherited material passing from one generation to the next?
No
What has both DNA and protein binding functionality?
Kinetochores
When would you expect to find bipolar spindle fiber attachment?
Metaphase of mitosis and meiosis 2
If there is a 1/2 chance of a child inheriting one syndrome and a 1/2 chance of the same child inheriting another syndrome, what is the probability that they will inherit either syndrome?
3/4
1/2+1/2 - (1/2*1/2) = 3/4
