Exam 1 review Flashcards
Alternate forms of a single gene
Allele
An allele whose phenotype is expressed in a Heterozygote, a trait that appears in the F1 hybrids (heterozygote resulting from matting between pure breeding parental strains showing antagonistic Phenotypes)
Dominant
An allele whose phenotype is not expressed in a Heterozygote, a trait that remains hidden in the F1 hybrids (resulting from the mating between pure breeding parental strains having antagonistic Phenotypes) appears in the F2
Recessive
A genotype in which the two copies of the gene that determine a trait are the same allele
Homozygous
A genotype in which the two copies of a gene that determine a trait are different alleles
Heterozygous
Hemizygous
a genotype for genes present in only 1 copy in an otherwise diploid organism (such as X linked genes in a male)
Actual alleles present in an individual
Genotype
An observable characteristic
Phenotype
Cross between parents differing in only one trait
Monohybrid cross
Cross between parents that differ in two traits
Dihybrid cross
A cross used to determine the genotype of an individual showing a dominant phenotype by mating with an individual showing the recessive phenotype
Test cross
A cross of an F1 individual with a parent or an individual with an identical phenotype to the parent
Back cross
Pure breeding individuals whose progeny in subsequent generations will be studied for specific traits
Parental, P
Progeny of the P generation that all look like the dominant parent, recessive gene is masked
First filial, F1
Progeny of F1 interbreeding, both parental types reappear in a 3:1 ratio, (3 dominant, 1 recessive), shows blending is not true
Second filial, F2
2 alleles for each trait separate (segregate) during gamete formation and then unite at random (one from each parent) at fertilization
Law of segregation
During gamete formation different pairs of alleles segregate independently of each other
Law of independent assortment
Dominance where a dominant allele completely masks the effect of the recessive allele in a heterozygous individual
Complete dominance
When an F1 hybrid does not resemble either pure breeding parent; an intermediate phenotype where both parental alleles contribute to the phenotype. Can produce up to 9 different Phenotypes. Shades of purple flowers.
Incomplete dominance
Both traits show up equally in the heterozygote’s phenotype in the F1 cross (spotted lentils) 1:2:1 in the F2 generation (blood group alleles; a & b sugars)
Codominance
DNA that encodes a protein or a particular type of RNA, basic unit of biological information (heredity)
Gene
Of ours in individuals who have inherited 2 recessive alleles of the H gene and do not produce the H carbohydrate that is the precursor to the A &B antigens. They may possess either or both alleles but are unable to express them. Look like type O. Recessive Epistasis.
Bombay phenotype
Phenomenon in which a single gene determines a number of distinct and seemingly unrelated characteristics
Plieotropy
Multifactorial trait
Determined by two or more factors including multiple genes interacting with each other or one or more genes interacting with the environment
Case of epistasis in which The epistatic allele is recessive. 9:3:4 labs
Recessive epistasis
Genes working in tandem to produce a particular trait 9:7 sweet pea flowers
Complementary Gene action
The effects of a dominant allele at one gene hides the effects of alleles at another gene 12:3:1 squash
Dominant epistasis 1 & 2
Genes whose products serve the same function in a pathway, a mutant phenotype is observed only if both gene products are absent 15:1 maize
Redundant genes
Indicates how many members of a population with a particular genotype shows the expected phenotype
Penetrance
The degree or intensity with which a particular genotype is expressed in the phenotype
Expressivity
Process in which heterozygosity for loss of function, mutant recessive allele for two different genes that function in the same pathway produces a normal phenotype (deafness) (albinism)
Complementation/noncomplementation
Cells in an organism other than gametes and their precursors
Somatic cells
Repeating pattern of cell growth (interphase, when chromosomes have been duplicated) followed by division (mitosis). (Letters)
Cell cycle, G2, M, G1, S
Interphase, gap before duplication, cell cycle
G1
Interphase, DNA Synthesis and chromosomal duplication, cell cycle
S
Interphase, gap before mitosis, cell cycle
G2
Mitosis: chromosomes condense, centrosomes move apart toward opposite poles and nucleoli begin to disappear
Prophase
Mitosis: nuclear envelope breaks down, sister chromatids are attached to the microtubules from opposite centrosomes (vocabulary: astral, kinetichore microtubules and polar microtubules)
Prometaphase
Mitosis: chromosomes align on the metaphase plate with sister chromatids facing opposite poles
Metaphase
Mitosis; centromeres (holding sister chromatids together) sever, kinetichore microtubules shorten and pull sister chromatids to opposite poles
Anaphase
Mitosis: identical sets of chromosomes are enclosed into nuclei. Nuclear membranes form around each set of chromosomes. Nuclei reform. Spindle fibers disappear. Chromosomes condense into chromatin.
Telophase
Mitosis: the cytoplasm divides. Begins during anaphase but not completed until after Telophase. Parent cells split into two daughter cells with identical nuclei.
Cytokinesis
Cells in an organism other than gametes and their precursors
Somatic cells
Specialized cells that incorporate into the reproductive organs where they ultimately undergo meiosis there by producing haploid gametes that transmit genes to the next generation
Germ cells
Specialized haploid cells (eggs and sperm for pollen) that carry genes between generations
Gametes
The visual description of the complete set of chromosomes in one cell of an organism usually presented as a Pictomicrograph with the chromosomes arranged in a standard format showing the size, number and shape of each chromosome type
Karyotype
(Homologs) chromosomes that match in size, shape and banding pattern; A pair of chromosomes containing the same linear gene sequence, each derived from one parent
Homologous chromosomes
The two identical copies of a chromosome that exist immediately after DNA replication. They are held together by protein complexes called cohesins.
Sister chromatids
Specialized chromosome region at which sister chromatids are connected and to which spindle fibers attached during cell division
Centromere
Microtubule Organizing center at the poles of the spindle apparatus
Centrosome
Process during which homologous chromosomes become aligned and zipped together; occurs in zygotene of prophase one
Synapsis
During meiosis, the breaking of one maternal and one paternal chromosomes, resulting in the exchange of corresponding sections of DNA and the rejoining of the chromosome. This process can result in the exchange of alleles between chromosomes.
Crossing over
Observable regions in which non-sister chromatids of homologous chromosomes crossover
Chiasmata
The process by which offspring derive a combination of alleles different from that of either parent; the generation of new allelic combinations, in higher organisms-> crossing over
recombination
Failures in chromosomal segregation during meiosis, responsible for such defects as trisomy
Nondisjunction
Chromosomes not involved in sex determination (we have 22 pairs of autosomes)
Autosomes
X and Y chromosomes in human beings, which determine the sex of an individual
Sex chromosomes
Condition in females caused by the presence of only one chromosome. They have short stature and other morphological abnormalities.
Turner syndrome
The production of sperm
Spermatogenesis
The formation of the female gametes (eggs)
OoGenesis
A condition caused by the presence of multiple X chromosomes in males. Tend to be excessively tall, feminized and sterile.
Klinefelter syndrome
Condition caused by complete or partial trisomy for the 21st chromosome, characterized by mental impairment and a variety of morphological abnormalities
Down syndrome
The proximity of two or more markers on a chromosome, the closer together the markers are, the lower the probability that they will be separated by recombination. Genes are linked when the frequency of parental type progeny exceeds that of recombinant progeny. Segregation law broken!
Linkage
A tetrad that contains for parental class haploid cells
Parental ditypes
A fungal tetrad containing for recombinant spores
Non-parental ditypes
Fungal ascus that carries four kinds of spores, or haploid cells, two different parental types and two different recombinant types
Tetratypes
A measure of interference in the formation of chromosomal crossovers during meiosis = actual double recombinant frequency/expected double recombinant frequency
Coefficient of coincidence
A parent crossing over between nonsister chromatids during mitosis
Mitotic recombination
Homologous chromosomes enter Synapsis, Crossing over, nuclear membrane breaks down and the spindle begins to reform
Meiosis: prophase I
Tetrads line up on the metaphase plate,
Meiosis: metaphase I
Centromere does not divide, chiasmata dissolve, homologous chromosomes move to opposite poles
Meiosis: anaphase I
The nuclear envelope reforms, each cell has one copy of each homologous pair
Meiosis: Telophase I
Similar to interphase but no chromosomal duplication takes place, cells separate
Meiosis: interkinesis
Centrioles move toward the polls, the nuclear envelope breaks down
Meiosis: prophase II
Chromosomes align at the metaphase plate, sister chromatids attach to spindle fibers from opposite poles
Meiosis: metaphase II
Centromere’s divide and sister chromatids move to opposite poles
Meiosis: anaphase II
Chromosomes begin to uncoil, nuclear envelopes and nucleoli reform
Meiosis: Telophase II
The cytoplasm divides forming 4 new haploid cells
Meiosis: cytokinesis
The phenotypic expression of an allele related to the sex chromosome of an individual
Sex linkage
The occurrence of one crossover reduces the likelihood that another crossover will occur in an adjacent part of the chromosome, crossovers not occurring independently
Chromosomal interference
The quantitative measure of the amount of interference in different chromosomes intervals by first calculating ______________________ defined as the ratio between the actual frequency of a double crossover observed in an experiment and the number of double crossovers expected on the basis of independent probability
Coefficient of coincidence (equals frequency observed divided by frequency expected)
Define interference
Interference = 1 - coefficient of coincidence, expressed as a decimal
Figure 3:14 suggested problem
Look at it
Difference between mitosis and meiosis
Short answer
Spermatogenesis and oogenisis
Compare contrast
Alter the phenotypes produced by alleles of other genes
Modifier genes (short tail gene in mice)
Independent assortment – chance governs which chromosomes are pulled to which poles in meiosis I.
Recombination – crossing over between homologues create different combinations of alleles within each chromosome
How meiosis contribute to genetic diversity
