lect 13: genes and the genome I Flashcards
what is the graph of the history of discoveries of DNA?
what are the learning objectives of this lecture?
-brief history of the discovery of DNA
DNA structure
-watson-crick proposal
-DNA structure provides a mechanism for heredity
chromosome structure
-levels of chromosome organization
-specialized nucleotide sequences
what are mendel’s laws of inheritance?
what is a gene?
a) a unit of a chromosome
b) a unit of inheritance
c) a unit of DNA
d) all of the above
b) a unit of inheritance
the law of independent assortment states that _____________
a) segregation of an allelic pair for one trait has no effect on segregation of alleles for another trait
b)an organism’s two alleles for a gene separate from one another during gamete formation
c)segregation of an allelic pair for one trait has a great effect on segregation of alleles for another
d) an organism’s three alleles for a gene separate from one another during gamete formation
a
what were key contributions to DNA’s discovery?
didn’t know about DNA until 1870
DNA structure needed to explain two things…..
-how genetic information is stored
-how genetic information is copied (and passed on to subsequent generations)
what is a nucleotide made out of?
what is the difference between a nucleotide and a nucleoside?
nucleotide
-deoxyribose sugar + base + phosphate group
-tide=tri (3 things)
nucleoside
-deoxyribose sugar + nitrogenous base
-doesn’t have a phosphate group
what does a DNA strand look like as building blocks?
what are the nitrogenous bases?
what is Chargaff’s rule?
complimentary base-pairing
what did rosalind franklin do?
used X-ray crystallography to discover the structure of DNA
what were the first two things in the watson-crick proposal?
- DNA is composed of two chains of nucleotides
- the two chains antiparallel, they run in opposite directions
what is the meaning of 5’ and 3’?
- the two chains are antiparallel, they run in opposite directions
5’ and 3’ describe which carbon the phosphate group is attached to
-5’ end=phosphate group attached to carbon 5
-3’ end= phosphate group attached to carbon 3
what were step 3 and 4 of the watson-crick proposal?
- the sugar-phosphate backbone is the exterior of the molecule, and the bases are interior
- bases are perpendicular to sugar-phosphate backbone (right angles)
what is the fifth step of the watson-crick proposal?
- the two chains form a spiral pair of right-hand helices
what are steps 6-10 of watson-crick proposal?
- DNA chains are held together by hydrogen bonds between bases
- pyrimidines always paired with purines
- double helix width 2nm
- only A-T and C-G pairs fit within double helix (2nm)
- complete turn is 10 base pairs
DNA strand with more C-G will be harder to break apart because more hydrogen bonds
what is the 11 step of watson-crick proposal?
- molecule has a major groove and a minor groove
what is step 12 of watson-crick proposal?
- complementary base sequences on each of the 2 strands (good explanation on how we can copy)
what are all the aspects of watson-crick proposal?
- DNA is composed of two chains of nucleotides
- the two chains are antiparallel, they run in opposite directions
- the sugar-phosphate backbone is the exterior of the molecule, and the bases are interior
- bases are perpendicular to sugar-phosphate backbone
- the two chains form a spiral pair of right-hand helices
- DNA chains are held together by hydrogen bonds between bases
- pyrimidines always paired with purines
- double helix width is 2nm
- only A-T and C-G pairs fit within double helix
- complete turn is 10 base pairs
- molecule has a major groove and a minor groove
- complementary base sequences on each of the 2 strands
the structure of DNA provides a mechanism for ____________
heredity
what is the central dogma of molecular biology?
RNA can also be the final product
in analyzing the number of different bases in a DNA sample, which result would be consistent with Chargaff’s findings?
a) A=G; G=T
b) A+G=C+T
c) A+T=G+T
d) A+C=G+C
b
what is eukaryotic DNA packaged into?
eukaryotic DNA is packaged into multiple chromosomes
-chromosome can be labeled with multicolored, fluorescent DNA probes that bind specifically to particular chromosomes
karyotype: homologous chromosome pairs ordered according to size
-pattern can be used to screen chromosomal abnormalities
what do chromosomes do?
organize and carry genetic information
what is the difference between a gene and a genome?
gene
-segment of DNA that contains instructions to make a particular protein or RNA molecule
genome
-the entirety of an organism’s DNA
grey areas= DNA used for other things that aren’t for protein coding
what are the levels of chromosome organization?
- chromosome=single, continuous DNA strand
- nucleosome
- chromatin fibers
- looped domains
what is the nucleosome?
-structural unit (of chromosome)
-DNA+histones
what is one of the most important functions of chromosomes?
protein synthesis
-most genes contain information to make proteins
what are other important functions of chromosomes?
specialized DNA sequences required for DNA replication and chromosome segregation
what is important in specialized DNA sequences?
replication origin
-site where DNA replication begins (what transcription machinery recognizes) (replication)
telomere: repeated nucleotide sequences at end (replication)
-replication of end of chromosome
-protective cap (ensures accurate replication and protects DNA from degradation)
centromere (segregation)
-role in separation of duplicated chromosomes
the behavior of what cell constituent correlated perfectly with that of Mendel’s genetic factors:
a) nucleolus
b) the endoplasmic reticulum
c) the homologous pairs of chromosomes
d) the homologous pairs of centrioles
c
during cell division, the nuclear material is organized into visible “threads” called ______
a) chromatids
b) mitochondria
c) chromophores
d) chromosomes
d
