Quiz 1 Flashcards
What are the three components of genomics?
structural, functional, comparative
What is functional genomics?
transcriptome, proteome, epigenome
What is structural genomics?
physical nature of genomes
What is comparative genomics?
conservation of genomic content across species
What did Mendel discover?
the basis of inheritance
Who was mendel and what did he do?
-Augustinian monk worked with pea plants in the 1860s
Why did mendel work with pea plants?
1) Distinct binary traits - color, shape
2) Can either self or cross pollinate
3) Large numbers of offspring
4) Pure breeding lines
What is a phenotype?
observable trait
What did mendel call genes?
determinants
How did Mendel explain the proportions 1:2:1 of the F3 generation of a purebreeding round x pure breeding wrinkled cross?
Proportions can be explained by:
- each plant carries one or both determinants
- determinants are deposited randomly into gametes: sperm or egg
- one determinant per gamete
- gametes then combine at random
What are alleles?
alternative forms of a gene
What is a genotype?
a set of alleles for a particular individual
What is Aa called?
heterozygote “hybrid”
What is aa or AA called?
homozygote
What are mendel’s laws?
1) for a single trait a gene pair separates into gametes at random and combines at random
2) for multiple traits, different gene pairs separate at random into gametes and combine at random (shape gene pair is independent of color gene pair)
- Inheritance of genes can be explained by probabilities
What is penetrance?
- the percentage of individuals with a particular genotype who exhibit the phenotype associated with that genotype
- have a population that you know have the same genotype, but not all of them show the phenotype expected of that genotype
What is an example of penetrance in humans?
BRACA-1 mutation - all have genotype but not all develop breast cancer
What is expressivity?
- extent to which a given genotype is expressed at the phenotype level
- same genotype range of phenotypes
What is incomplete dominance?
phenotype of the heterozygote is intermediate to the two homozygous forms (pink Aa)
What is codominance?
heterozygote displays both of the homozygous phenotypes
What is linkage?
When genes are physically located on the same chromosome
What are chromosomes?
threadlike structures of nucleic acids and proteins found in the nucleus of most living things
What are some important characteristics of chromosomes?
they are observable and possess interesting behavior during cell divisions
Each species has a stable number of ______
chromosomes
How many chromosomes do human somatic cells have?
46 chromosomes, 22 pairs of autosomes, 1 pair of sex chromosomes this is the diploid number (2n), 1/2 of each pair comes from the mother and half from the father
How many chromosomes do sex cells have?
23 chromosomes, haploid number (n), unpaired chromosomes
What is mitosis?
nuclear division of somatic cells
What is the cell cycle?
- G1 phase (growth or gap)
- S phase (synthesis) DNA is replicated
- G2 phase (growth or gap)
- M phase (mitosis)
What makes up interphase?
G1,G2,S
What is the chromosome number in interphase? Prophase?
2n, 4n
What are two key things to remember about mitosis?
Replication of chromosomes, followed by segregation, produces two identical daughter cells
What is meiosis?
2 successive nuclear divisions that make sex cells
What are the four steps of meiosis?
1) DNA replication 2) Homologous chromosome pairing 3) Segregation 4) Segregation
What did Walter Sutton and Theodore Boven study/hypothesize?
- the behavior of Mendel’s particles parallels the behavior of chromosomes during meiosis
- Sutton-Boven Hypothesis - genes are physically located on chromosomes
How did Sutton and Boven defend their hypothesis? (What are three similarities between genes/alleles and the process of chromosome segregation?)
1) Genes and chromosomes both come in pairs (mom/dad and Aa)
2) Alleles of gene pairs and a member of a homologous pair of chromosomes both segregate equally into gametes
3) Different gene pairs and different sets of chromosome pairs act/segregate independently
What is the problem with the Sutton-Boven hypothesis?
correlation does NOT equal causation
What are Drosophila Melanogaster and who studied them?
fruit fly, Thomas Hunt Morgan 1900s
Why were Drosophila used for genetic studies?
easy to raise, cheap, produce lots of offspring, have observable traits
Explain the chromosome number of drosophila melanogaster.
- 4 pairs of chromosomes
- diploid = 8 chromosomes (4x2) (2n)
- haploid = 4 chromosomes (n)
Why dont white eye female fruit flies exist as commonly as males?
eye color trait is sex linked - physically located on the X chromosome
How do you determine litter size?
1 / probability of genotype or phenotype - if it is not an even number round up to find litter size
What are some charateristics of meiosis?
- separation of homologous pairs
- 4 daughter cells (haploid)
- 2 divisions
- germ cells, polar bodies
What are some characteristics of mitosis?
- separation of sister chromatids
- 2 daughter cells (diploid)
- 1 division
- somatic cells
What was Griffiths experiment?
- (1928)
- bacteria Streptococcus pnemonaie
- S-strain: smooth and lethal R-strain: rough and non-lethal
- infect mouse with S strain - die
- infect mice with heat killed S strain - live
- infect mice with heat killed S strain and live R strain - die
- concept of transformation
What was Avery, Macleod, and McCarthy’s experiment?
(1944)
-showed that DNA is the active component of the transforming principle that converted R bacteria into lethal bacteria when mixed with the S strain
What was the Hershey and Chase experiement?
(1952)
- used radiolabelling to show that when bacterial culture is infected with bacteriophages (a virus) DNA is the major component that enters the cells
- labelled the sulphur in protein and phosphorus in DNA
- agitated in blender - found radioactive phosphorus in cell (indicating the presence of DNA)
What is DNA
- deoxyribonucleic acid
- linear, unbranched polymer made up of four chemically distinct subunits (nucleotides)
What makes up a nucleotide?
sugar (deoxyribose), nitrogenous base (1’), phosphate group (5’)
What are the two groups of nitrogenous bases?
Purines - Adenine and Guanine (2 rings)
Pyrimidines - Cytosine and Thymine (1 ring)
What are nucleotides connected by?
- phosphodiester bonds
- new nucleotides must be added to the 3’ OH terminus
- 5’ -> 3’ is the directionality of DNA
What did Watson and Crick already know when they began to solve the structure of DNA?
1) DNA was composed of multiple polynucleotides
2) base ratio - chargaffs rule
What strategy did Watson and Crick use to study the structure of DNA? Who’s image did they use?
X-Ray diffraction- crystallize your model of interest
- Rosalind Franklin - photo 51
What structure did Watson and Crick suggest?
double helix
Describe the structure of DNA
- Double helix
- two strands are antiparallel
- electrostatic interactions
- base stacking stabilizes the molecule
What were three models for the replication of DNA?
conservative - both strands completely replicated
semi-conservative - one strand replicated using one strand as a model to form a new DNA molecule with one new and one old DNA strand
dispersive- random segments replicated
What was the Meselson and Stahl experiment?
- used a heavy isotope of N (N15) in E. Coli bacteria
- grew the cells on lighter nitrogen for 1 or 2 generations
- isolated DNA and ran on a cesium gradient to identify the weights of the new and old DNA strands
- after 1 gen - medium band (ruled out conservative)
- after 2 gen - 2 bands (ruled out dispersive)
How is DNA replication controlled?
tightly controlled, must occur with high fidelity to prevent introducing mutations