MCAT BIO CH. 7 PART 1 Flashcards
What are allosomes?
Sex chromosomes
What are homologous chromosomes?
One from the mother, one from the father, two nonidentical copies of a chromosome
What are alleles?
Different versions of genes
What is meiosis?
Cell division that reduces the number of copies of each chromosome from two to one (forming haploid cells)
What cells in males and what cells in females undergo meiosis?
Spermatogonia, oogonia
What occurs in meiosis to share genomic content?
Recombination between homologous chromosomes
What is the product of meiosis?
4 haploid cells
What is different with prophase I in meiosis and mitosis prophase?
Homologous chromosomes pair with each other in synapsis
The paired homologous chromosomes are called….?
Bivalent or tetrad
Which meiosis state takes the longest and why?
Prophase I since crossing over is complex
What protein assist in the formation of tetrad during synapsis?
Protein structure called synaptonemal complex (SC)
How does the SC assist with homologous chromosomes, how does it start?
Proteins SYCP2 and SYCP3 attach to each of the two homologous chromatin structures that are to be paired
What is the lateral element of the SC?
Proteins that have attached to each of the two homologous chromatin structures
What occurs when the lateral elements of the SC are produced?
Align and attach via. centra region made of SYCP1 and other proteins
What do the lateral region and central regions form, based on crossing over?
They form the SC and work like a zipper to connect homologous chromosomes
What is different between metaphase I and metaphase in mitosis?
Tetrads are aligned at the center of the cell while in mitosis, sister chromatids are aligned
What is different between anaphase I and metaphase in mitosis?
Homologous chromosomes separate and chromatids remain together
What happens in telophase I?
Cells divides into two cells
What are the cells considered in telophase I, based on ploidicity?
Haploid; each cell has a single set of chromosomes
DNA replication occurs between meiosis I and II. T/F
False
The movements of chromosomes are the same in meiosis II and mitosis except that….?
Meiosis II has a haploid number of chromosomes mitosis has a diploid number
What happens at the end of telophase II?
Four haploid cells are produced from a. single diploid parent cell
What is nondijustion?
Homologous chromosomes or sister chromosomes failing to separate during meiosis
What is trisomy?
Gamete with two copies create a zygote with three copies of a chromosome
What is monosomy?
Gamete with no copies create a zygote with one copy of a chromosome
What is an example of nondisjunction not being lethal in humans?
Trisomy of chromosome #21 results in Down syndrome
What is an example of nondisjunction in sex chromosomes being nonlethal?
Turner syndrome: organisms with 1 X and no Y
What are the two laws of Mendel?
- Law of segregation
2. Law of independent assortment
What is the law of segregation?
Two alleles of an individual are separated and passed on to the next generation singly
What is the law of independent assortment?
Alleles of one gene will separate into games independently of alleles for another gene
What is a test cross?
individual is crossed to another individual that has a homozygous recessive genotype
If the color gene and the shape gene are right next to each other on a chromosome, will they display independent assortment?
They would display an exception called linkage
What tool is used to visualize law of segregation and independent assortment?
Punnett square
What are to ways to determine the probabilities of an outcome in a cross?
- Rule of multiplication
2. Rule of addition
What is the rule of multiplication?
Probability of two independent evens occurring found by multiplying the odds of either event alone
What is the rule of addition?
Used to calculate the chances of either of two events happening
What is incomplete dominance?
Phenotype of a heterozygote is a blended mix of both alleles
What is codominance?
Two alleles are both expressed but not blended
Other than ABO, what other main antigen is used in blood typing?
Rh (rhesus) factor
What is the pattern of the Rh blood factor?
Rh^DRh^D or Rh^DRh^d (RRand Rr) are Rh positive and RhdRhd are Rh negative
What is pleiotropism?
Expression alters many different aspects of the organism’s total phenotype
What is polygenism?
Traits influenced by many difference genes are polygenic
What is penetrance?
The likelihood that a person with a given genotype will express the expected phenotype
What type of penetrance can alleles or mutations display?
High, incomplete or low penetrance
What is epistasis?
Expression alleles for one gene is dependent on a different gene
What are recessive lethal alleles?
Mutant alleles can cause death of an organism when present in a homozygous manner
What is linkage?
Failure of genes to display independent assortment, located on the same chromosome
The frequency of recombination between two genes on a chromosome is proportional to….?
The physical distance between the genes along the linear length of DNA molecule
The frequency of recombinations given by….?
The number of recombinant phenotypes resulting from a cross divided by the total number of progeny
What is the equation of recombination frequency? (RF)
RF = # of recombinants / total # of offspring
What are the two types autosomal trait patterns?
- Autosomal dominant
2. Autosomal recessive
What are mitochondrial traits?
Inherited via the mitochondrial genome through the cellular material contributed by the mother
What does hemizygosity means and what’s an example?
The individual only has one copy of the chromosome in a diploid organism; mitochondrial traits
Mitochondrial genome are usually given the prefix…?
mt
Why are Y-linked traits rare?
The Y chromosome is small and contains small number of genes
Many of the genes on the Y chromosome are….?
Sex determination
What is an example of an X-linked recessive trait?
Hemophilia
Based on X-linked traits, an allele that encodes inactive protein or no protein is generally….. (recessive or dominant)?
Recessive
Females affected by a mitochondrial trait, which offsprings will be affected?
All offsprings are affected, sons or daughters
What does population genetics consider?
Inheritance of traits in populations over time
What is a gene pool?
The sum total of all genetic information in a population
What is the Hardy-Weinberg law?
Frequencies of alleles in the gene pool of a pop’n won’t change over time if they follow the assumptions
What are the assumptions to the Hardy-Weinberg law?
- No mutation
- No migration
- No natural selection
- Random mating
- Pop’n large to prevent random drift
What is the Hardy-Weinberg equation?
p^2 + 2pq + q^2 = 1
When does a population reach Hardy-Weinberg equilibrium?
After one generation
What is fitness in relation to evolution?
How successful it is in passing on its alleles to future generations
Can natural selection cause new alleles to appear in the populations?
No, it cannot alter introduce genetic diversity
What are the two new sources of genetic variation in a population?
New alleles and new combinations of existing alleles
What is directional selection?
Natural selection removing the extreme and population average move in one direction over time
What is divergent selection?
Natural selection removes the members near the average, leaving the extremes
What is stabilizing selection?
Both extremes of traits are selected against, driving population closer to average
What is artificial selection?
Human intervene in the mating of animals and plans to achieve desired traits through controlled mating
What is sexual selection?
Animals have evolved rituals and physical displays that-lay key roles in attracting and choose a mate
What is kin selection?
Animals that live socially share alleles with other individuals and may sacrifice themselves for the sake of the alleles they share with another individual
What is a specie?
A group of organisms which are capable of reproducing its each other sexually
What is the difference between a specie and a population?
Species can mate and produce fit offspring, populations do
What are two types of reproductive isolations?
Pre-zygotic and post-zygotic
What are the five prezygotic barriers?
- Ecological
- Temporal
- Behavioral
- Mechanical
- Gametic
What is the ecological prezygotic barrier?
Cannot access each other; different living areas
What is the temporal prezygotic barrier?
Different times of the day, season or year
What is the behavioural prezygotic barrier?
Special rituals or courtship behaviors before mating
What is the mechanical prezygotic barrier?
Reproductive structures are not compatible
What is the gametic prezygotic barrier?
Sperm from on species cannot fertilize egg of another
What are the three postzygotic barriers?
Hybrid: 1. Inviability 2. Sterility 3. Breakdown
What is the hybrid inviability barrier?
Offspring do not develop or mature normally
What is the hybrid sterility barrier?
Hybrid is born but cannot reproduce
What is the hybrid breakdown barrier?
Second generation hybrid is biologically defective
What is speciation?
Creation of new species
What is cladogenesis?
Branching speciation; one species diversifies and becomes two or more species
What is anagenesis?
One biological species becomes another by changing so much over time
What type of speciation is allopatric isolation?
Cladogenesis
What is allopatric isolation?
Geographical isolation leads to reproductive isolation
What is sympatric speciation?
A species gives rise to a new species in the same geographic area through divergent selection
What are homologous structures?
Shared features resulted from a common ancestor
What are analogous structures?
Structures serving the same function in two different species but not due to common ancestor
What is convergent evolution?
Two different species come to posses many analogous structures due to similar selective pressures
What is divergent evolution?
Opposite of convergent evolution; causes cladogenesis
What is parallel evolution?
Two species go through similar evolutionary changes due to similar selective pressures
What is taxonomy?
Biological classification
In binomial classification, each specie is given two name: ….?
A genes and a species; gene is always capitalized and species its not
What are the eight principal taxonomic categories?
Domain, Kingdom, Phylum, Class, Order, Family, Genus and Species
What is the mnemonic for the taxonomic categories?
Dum King Philip Came Over For Great Sex
What does anterior facing means? What about posterior?
Front-facing; back-facing
What is ventral based on bilateral symmetry?
Opposite of dorsal; belly button
In humans, based on bilateral symmetry, what is superior? What is inferior?
Towards the head, towards the feet
What is another way of saying towards the head other than superior? What about another way of saying inferior based on bilateral symmetry?
Cephalad; caudal
It is through that the early atmosphere was what? Based on that, how did it effect electron donors?
Reducing environment; electron donors were prevalent
What is abiotic synthesis?
Monomers spontaneously formed through rocks and clay acting as catalyst
Polypeptides made through abiotic synthesis are called: ______?
Proteinoids
What do proteinoid form in water?
Microspheres; droplets
What happens when lipids are added to the solution of water and protenoids?
Liposomes ad lipids forming a layer on the surface of proteins
What are coacervates?
Complex particles including polypeptides, nucleic acids and polysaccharides
What are examples of protobionts?
Microspheres, liposomes and coacervates
What did protobionts lacked?
Organized mechanic of heredity
