Genetics Introduction Flashcards
What is the study of heredity and variation?
Genetics
The differences in characteristics of individuals, this is also the raw material for evolution but has no adaptive advantage
Variation
How is sickle cell anemia advantageous to places where malaria is common?
There is a increase in resistance to malaria because of only having 1 copy of the mutated allele
Dominant or Non-dominant: Tounge roller
Dominant
Dominant or Non-dominant: Cleft Chin
Dominant
Dominant or Non-dominant: Dimples
Dominant
This is the sum total of genes or the genetic makeup of an individual
Genotype
This is the sum total of characteristics or traits
Phenotype
What are the 4 types of characteristics?
Morphological or anatomical, physiological, sexual, and behavioral
Type of characteristic: type of cell, shape of organ or cells etc
Morphological
Type of characteristic: function eg. issues with cancer, tubercolosis
Physiological
Type of characteristic: primary and secondary characteristics eg. development of gonads, mammary glands and pubic hair
Sexual
What are the identifying characteristics of male Drosophila melanogasters?
Smaller in size, black and rounded abdominal segment, bears a sex comb on first thoracic leg, thorax contains wings
What are the identifying characteristics of female Drosophila melanogasters?
Larger size, posterior abdominal segment is transparent with pointed protruding plate, absent sex comb, hind wing in folded condition more extended
Type of characteristic: down syndrome, psychological and mental disorders
Behavioral
An example of behavioral characteristic that exhibits light skinned pigmentation and mental retardation, this is also an inborn error in metabolism which can be detected at birth
Phenylketonuria
What is the gene involved in phenylketonuria that has multiple effects?
Pleiotropic gene
When this enzyme is not produced thus causing the accumulation of phenylalanine
Phenyl hydroxylase
This can become toxic that can break down brain cells causing mental retardation
Phenylpyruvate
Tyrosine is converted to melanin but without the phenylalanine hydroxylase, what does it cause?
Fair skinned pigmentation
At what phase of the cell cycle does duplication occur?
S phase
What do you call a chromosome without a centromere?
Acentric
What happens to acentric chromosomes during anaphasic movement?
It lags and eventually becomes lost
What is a homologous chromosome?
It is 2 duplicated chromosomes containing the same genes, however it could also contain different variations of the same gene
When are homologous chromosomes divided?
During meiosis 1
What is a sister chromatid?
It is 1/2 of the duplicated chromosome, they also contain the exact same copy of genes
When are sister chromatids divided?
During meiosis 2
What is the other term for alleles?
Allelomorphs
What are homologous chromosomes composed of?
1 paternal and 1 maternal chromosomes
What are the different characteristics of chromosome morphology?
Size, position of the centromere, banding patterns, and presence of secondary constrictions or satellites
Chromosome morphology: long, medium, short or small
Size
Chromosome morphology: metacentric , sub metacentric, acrocentric, telocentric
Position of the centromere
What do you call when the centromere is at the center of the chromosome resulting to equal arms and appears as a V shape during anaphase?
Metacentric
When the centromere is on one side or sub median, and it is in either a V shape or J shape during anaphase, what is it called?
Sub metacentric
When the centromere is located close to one end, are called sub terminal, and produces a j or rod shape, what is it called?
Acrocentric
These are unstable where the centromere appears to be at the end of the chromosome, this is also called a terminal rod shape during anaphase
Telocentric
Why are there visible banding patterns in chromosomes?
Some materials are more condensed than others, thus the darker stain in some parts
What do you call the light areas of the chromosome?
Euchromatin
What is a heterochromatin?
This is the darkly stained areas in a chromosome
What are the 4 common staining procedures?
G-banding, Q-banding, R-banding, C-banding
What banding technique treats metaphase spreads with trypsin, is stained with giemsa stain, and is observed under a light microscope?
G-banding (appearance of darkly stained G bands)
What is trypsin?
An enzyme that digest part of chromosomal protein
What is done in Q-banding?
The metaphase spread is treated with the chemical quinacrine mustard, and is observed under a special ultraviolet light microscope thus the bright fluorescent bands upon exposure but appears similar to G banding pattern
This is the reverse of G-banding
R-banding
The metaphase spread is heated at high temps to achieve partial denaturation of DNA, this is also stained with giemsa and is observed under a light microscope
R-banding
What is C-banding?
The metaphase spreads are chemically treated to extract DNA from the arms but not the cemtromeric regions. This is also stained with giemsa and is also observed under a light microscope
What does the darkly stained C band centromeric region corresponds to?
Region of constitutive heterochromatin
How is karyotyping done?
After blood extraction, phytohemagglutinin (PHA) and culture medium is added which is then cultured at 37 celsium for 3 days, after this, colchicine is added and hypotonic saline. The cells are fixed and spread onto slides by dropping. They are then digested with trypsin and stained with giemsa. The spread is then analyzed to produce the karyotype
What is phytohemagglutinin (PHA)?
This is a mitogen that stimulates mitosis
This arrests spindle fiber formation
Colchicine
What do you call the karyotyping of fetal cells?
Amniocentesis
What are nucleolar organizing regions?
These are chromosomal regions that are crucial for the formation of the nucleolus
Chromosome morphology: nucleolar organizing regions
Presence if secondary constrictions/satellite
This is a diagrammatic representation of the karyotype that shows all pairs of homologous chromosomes in the nucleus. The centromeres a re aligned and the short arm is uppermost
Idiogram
What are the 2 parts of the cell cycle?
The interphase and mitosis
What are the 3 stages in interphase?
Gap 1, S phase, and Gap 2
What happens during G1?
Growth
What happens during S phase?
Growth and DNA replication
What happens during G2?
Growth and final preparations for division
The process that forms the gametes
Meiosis
This is reductional in nature so gametes have half of the chromosome number
Meiosis 1
Why is meiosis 2 equational in nature?
This is because the haploid gametes from meiosis 1 are joined together during fertilization re-establishing the diploid condition
What are the different stages if prophase 1
Leptotene, zygotene, pachytene, diplotene, diakinesis
This is when synapsis or the pairing of homologous chromosomes occur
Zygotene
This is when crossing over or recombination occurs that is 1 mechanism of variation
Pachytene
What happens during metaphase 1?
Random arrangement of paternal and maternal chromosomes at the metaphase plate. This is also the 2nd mechanism in enhancing variation
This is when the chromosomes move to opposite poles and no duplications occurs yet
Anaphase 1
When is the binomial equation used?
To determine the number if chromosomally different types of gametes and the types and frequency of each type of gamete
What is the probability of obtaining a paternal or maternal chromosome in the gamete from one homologous pair of chromosomes
1/2
The probability of 2 independent events occurring together is equal to the product of their individual probabilities
Product rule of probability
What is the sum rule of probability?
This is the probability of 2 mutually exclusive events occurring together is equal to the sum of their individual probabilities.
What does 2n=4 mean?
There are 2 sets of chromosomes with 2 chromosomes per set
What do you call a pair of synapse chromosome?
Bivalent/synaptonemal complex
What is the relevance of duplication of chromosomes?
This is to maintain chromosome number, and for the daughter cells to be genetically identical to the parents
What do you call the position occupied by a gene?
Locus
_______ should occupy the same locus in the pair of homologous chromosomes
Alleles
What are examples of alleles?
Eye color, hair color, height, weight, IQ
When are genes not an exact copy?
During the presence of the formation of the gametes and during crossing over
What do you call the color coded type of karyotyping?
Spectral karyotyping
This plays a role in nucleolus reformation after division
NORs
Eggs undergo________
Senescence
When are oocytes arrested? (Continued during puberty)
Prophase 1
What is the urinary bladder of a fetus?
Allantois (also for waste)
What can be detected in karyotyping?
Genetic disorders, chromosome number, sex, chromosomal aberrations
When is there value in polyploidy?
For plantae
What effect does the 2 mechanisms for variation have on the daughter cells?
This allows them to be chromosomally different, making them genetically different
