Introduction, Chromosome Structure, Mitosis Flashcards
Genome:
Is a complete set of genetic instructions for any organism
Can either be RNA or DNA
Who was Archibald Garrod?
First to recognize that albinism was an inheritable trait that was located on a specific chromosome
The coding system for genomic information is _______?
Very similar among organisms
What are the three major subdivisions of genetics?
Transmission, molecular, and population genetics
What is transmission genetics?
Encompasses basic principles of heredity and how traits are passed from one generation to the next
What is molecular genetics?
Concerns the chemical nature of the gene itself and how genetic information is encoded, replicated, and expressed
What is population genetics?
Explores the genetic composition of groups of individual members of the same species and how that composition changes geographically and with the passage of time. It is fundamentally the study of evolution
What are the early theories relating to inheritance?
Pangenesis, inheritance of acquired characteristics, preformationism, and blending inheritance
What is pangenesis?
Developed by Greek philosophers Specific particles (gemmules) carry information from various parts of the body to reproductive organs (sperm,egg), from which they are passed to the embryo at the moment of conception
What is the Germ-plasm theory?
According to the germ-plasm theory, germ-line tissue in the reproductive organs that contains a complete set of genetic information that is transferred directly to the gametes
What is the inheritance of acquired characteristics theory?
Primarily made famous by Lamarck
Traits acquired in a person’s lifetime become incorporated into that person’s hereditary information and are passed on to offspring
What is the theory of preformationism?
According to preformationism, inside the egg or sperm there exists a fully formed miniature adult, a homunculus, which simply enlarges in the course of development.
Preformationism meant that all traits were inherited from only one parent
What is the theory of blending inheritance?
Offspring are a blend of parental traits and the genetic material itself blends. Once blended, genetics differences cannot be separated out in future generations.
**yellow+blue=green; cant separate green to get yellow and blue again
What is cell theory?
All life is composed of cells, and cells arise only from cells
What is mendelian inheritance?
Traits are inherited in accord with defined principles
What early concepts of heredity are correct?
Germ-plasm theory, cell theory and mendelian inheritance
What are the top 6 model genetic organisms?
Drosophila melanogaster - Fruit fly Escherichia coli - Bacterium Caenorhabditis elegans - Nematode Arabidopsis thaliana - Thale-cress plant Mus musculus - House mouse Saccharomyces cerevisiae - Baker's yeast
What are model genetic organisms?
Organisms with characteristics that make them useful for genetic analysis
What properties, in general, make the top 6 organisms valuable as model genetic organisms?
Short generation time
Production of numerous progeny
The ability to carry out controlled genetic crosses
The ability to be reared in a laboratory environment
The availability of numerous genetic variants
There is an accumulated body of knowledge about their genetic systems
How can studying genetic model organisms help in understanding human genetics?
Research on bacteria, yeast, insects, worms, fish, rodents and plants has shown that the basic operating principles are nearly the same in all living things. So a finding made in fruit flies can shed light on a biological process in people.
What are two basic types of cells?
Eukaryotic and prokaryotic
What is the fundamental unit of heredity?
Gene
A gene that specifies a characteristic may exist in several forms called ______?
Alleles
Genes, along with environmental factors, determine what?
Expression of traits.
**Genes confer phenotype
What is genetic information carried in?
RNA and DNA
Where are genes located?
Chromosomes
How do chromosomes separate?
Through the processes of mitosis and meiosis
Where is genetic information from DNA transferred to?
To RNA then to protein
What are mutations?
Permanent changes in genetic information that can be passed from once cell to another or from parent to offspring
What is evolution?
Genetic change
Some traits are affected by what? Give an example
by multiple genes that interact in complex ways with environmental factors. Human height, for example, is affected by hundreds of genes as well as environmental factors such as nutrition.
Gene:
an inherited factor that determines a characteristic.
Allele:
One of two or more alternate forms of a gene
Phenotype
The appearance or manifestation of a character
Genotype
Set of alleles possessed by an individual organism
Chromosome
A thread-like structure of nucleic acids and proteins, carrying genetic information in the form of genes
Mitosis
A type of cell division that results in two alike daughter cells
Meiosis
A type of cell division that results in four daughter cells with half the number of chromosomes as the parent
Flow of genetic information
DNA——–>RNA———>Protein
What are the characteristics of prokaryotes?
- Nucleus is absent
- 1 to 10um in diameter
- Usually a single circular DNA molecule
- Histones absent in eubacteria, but is in some archaea
- Small amount of DNA
- No membrane-bound organelles
- No cytoskeleton
What are the classes of prokaryotes?
Eubacteria and Archaea
What types of cells can be unicellular or multicellular with membrane-bound organelles?
Eukaryotes
What are some of the implications of all organisms having similar genetic systems?
a. That all life forms are genetically related
b. That research findings on one organism’s gene function can often be applied to other organisms
c. That genes from one organism can often exist and thrive in another organism?
d. All the above
d. all the above
Define the term:
Inherited determinant of the phenotype
Elements that control traits
Located at a specific position on a chromosome referred to as a locus
Gene
Describe prokaryotic cell reproduction
Simple division: separation of replicated circular chromosome
Origin of replication
There is a high rate of replication
What are the characteristics of eukaryotes?
Membrane-bound nucleus 10-100um in diameter Multiple linear DNA molecules Histones Large amount of DNA Membrane-bound organelles Cytoskeleton
What are eukaryote chromosomes associated with?
Histones to form tightly packed DNA
What is DNA + histones?
chromatin
What doe histone proteins limit?
Accessibility of enzymes and other proteins to copy and read DNA
What doe Histones enable?
DNA to fit within the nucleus
What must eukaryotic DNA be separate from before genetic information can be accessed?
Histones
Homologous chromosomes:
Two chromosomes of a pair share the same loci. Eukaryotic chromosomes are typically found in pairs
A set of chromosomes consists of what?
One member of each pair of chromosomes
Diploid cells
Two complete sets of chromosomes
Haploid (monoploid)
Cell has a single complete set of chromosomes
Tetraploid
Cells that have four complete sets of chromosomes
Triploid
Cells that have three complete sets of chromosomes
Centromere
Serves as the attachment point for spindle microtubules
What are the four classes of chromosome location?
Metacentric, submetacentric, acrocentric, telocentric
Short arm of a chromosome is called a ______
p arm
Long arm of a chromosome is called a _____
q arm
How many pairs of chromosomes do humans have?
23
One chromosome can be either ______ or _______
One chromatid or two sister chromatids
What are the stable ends of chromosomes?
Telomeres
What is a constricted region of the chromosome where the kinetochores form and the spindle microtubules attach?
centromere
What are four characteristics of telomeres?
Located at the natural ends of a linear chromosome
Provide chromosome stability
May limit cell division
May play a role in aging and cancer
What is a telomerase? What is its function?
A ribonucleoprotein that is an enzyme that adds DNA sequence repeats (TTAGGG).
It allows the DNA to be completely replicated; preventss shortening of chromosome
Origins of replication:
Are sites where DNA synthesis begins
What are the 2 major results of mitosis?
There is usually an increase in cell numbers
The resulting daughter cells are genetically identical
During embryonic development, what does mitosis produce?
Produces a stockpile of cells for embryogenesis
Organismal growth occurs through what process?
Mitotic activity (hyperplasia)
What provides a mechanism for the replacement of damaged or worn-out cells?
Mitosis
The cell cycle consists of a number of stages that are a part of a continuum. Name the stages
G-0 phase G-1 phase S phase G-2 phase M phase
What are the stages in the cell cycle that are a part of Interphase?
G-1, S, and G-2
What are the G-1 phase activities?
First gap/growth phase
Concentration of G-1(s)-cyclins increases
G-1-cyclin binds to inactive cdc2 kinase
MPF is activated at the end of this phase and leads to activities needed for DNA synthesis
Which stage is highly variable with regard to time?
G-1 phase
What is the G-0 phase?
Term used to describe the condition of a cell that has been taken out of the classical cell cycle
What are the S phase activities?
DNA synthesis Chromosome replication G-1-cyclins degraded cdc2 kinase inactive B(M)-cyclin concentration begins to increase towards end of S phase
How long does the S phase last?
About 7 hours
What are the G-2 activities?
Further preparation for mitotic division
B(M)-cyclins bind to cdc2 kinase
Activated MPF leads to activities necessary for mitosis
How long does G-2 phase last?
about 2 hours
What activities happen during M phase?
Prophase, metaphase, anaphase, telophase
B(M)-cyclin is degraded towards the end of the phase
Cdc2 kinase becomes inactivated
How long does the M phase lasts?
.7 hours
What state are the chromosomes in during Interphase?
Decondensed
Before the S phase of cell cycle, each chromosome consists of _______
1 chromatid
After S phase of a cell cycle, each chromosome consists of ________
2 chromatids bound by centromere
What are prophase activities?
Centrioles move to opposite poles
Spindle apparatus is organized
Nuclear membrane begins to disintegrate
Chromosomes become condensed
When are chromosomes visible as separate entities with light microscope?
During Mitosis when they become condensed
What are the metaphase characteristics?
Chromosomes are located at center of cell along equatorial plate (usually)
Spindle fibers are attached to kinetochores
Centromeres divide at the end of metaphase
Chromosome number has doubled
What happens during Anaphase?
Daughter chromatids move to opposite poles
What happens during Telophase?
Chromosomes begin to uncoil
Nuclear membranes reform
Cytokinesis usually occurs and two daughter cells are separated
What happens if cytokinesis does not occur?
There many still be two nuclei, but they will be located in a single cell (endomitosis)
What are characteristics of embryonic cells?
These cells proceed immediately to the next cell cycle with little time in the G-1 phase
Cell does not grow or differentiate
What are examples of embryonic cells?
Embryonic cells and some types of tumor cells
What are characteristics of labile cells?
These cells spend more time in the G-1 stage and grow and become differentiated
What are examples of Labile cells?
Epithelial cells in the gut lining and epidermis
Hematopoietic cells
What stage are non-dividing cells in?
These cells become permanently locked in the G-1 stage and never divide again
What are examples of non-dividing cells?
Skeletal muscle cells, cardiac muscle cells, neurons
Karyokinesis:
Physical division of nuclear material
Cytokinesis:
Physical division of cytoplasmic material
Endomitosis:
Karyokinesis is not followed by cytokinesis
What does endomitosis result in?
An increase in ploidy
Ploidy:
Increase in complete sets of chromosomes
