DNA Structure and Functions
The structure of a DNA has _'carbon of a sugar is joined by a phosphate group to __' carbon of next sugar, forming __ sugar-phosphate backbones running in _______ directions
3,5,2,opposite
Describe a Eukaryotic Chromosome.What is a chromosome? Name all it's functions.
- All organisms pass DNA to offspring when they reproduce - In cells, each DNA molecule is organized as a chromosome - A chromosome: 1) Is a structure that consists of DNA and associated proteins, 2) Carries part or all of a cell's genetic information, and 3) Eukaryotic cells have a number of Chromosomes.
What do DNA nucleotides consist of?
1) A DNA nucleotide has a five-carbon sugar, three phosphate groups, and one of four nitrogen-containing bases
1)What is the DNA sequence? What does it represent?
1) The order of nucleotide bases in a strand of DNA - the DNA sequence - is genetic information • Descendant cells must get an exact copy of DNA • When the cell reproduces, it must contain two sets of chromosomes: one for each of its future offspring • DNA duplicates itself by DNA replication
American biologist ______ and British biophysicist ______ suspected that the DNA molecule was a helix. They argued about the size, shape, and bondingrequirements of the four DNA nucleotides
1)American biologist James Watson and British biophysicist Francis Crick.
1)DNA consists of two backbones of ______+_______. 2) Genetic info is stored in the sequence of _____. These ______ protrude from these backbones and connect the two strands.
1. Sugar (Deoxyribose) + Phosphate (3) 2. bases
DNA synthesis occurs in the __' to __' direction
5 to 3
what is a sister chromatid?
A duplicated chromosome consists of two long, tangled filaments (sister chromatids) bunched into an X shape
Name the 4 DNA nucleotides. 2) What were Erwin Chargaff's rules? 3) ______ in base sequence are the source of life's diversity
1) Adenine, guanine, cytosine, thymine 2)1950s: Erwin Chargaff made two discoveries: • Chargaff's first rule: A = T and G = C (amounts of thymine and adenine in all DNA are the same, as are amounts of cytosine and guanine) • Chargaff's second rule: Proportions of adenine and guanine differ among the DNA of different species 3) Variation
1) _____ and ______ tested whether genetic material injected by bacteriophages into bacteria is DNA,protein, or both. 2) What is a bacteriophage?
1) Alfred Hershey and Martha Chase 2) Virus that infects bacteria
Describe how chromosomes duplicate. Draw and Label a chromosome duplication.
During most of a cell's life, each of its chromosomes consists of one DNA molecule • As it prepares to divide, the cell duplicates its chromosomes, so both offspring get a full set • After chromosomes are duplicated, each consists of two DNA molecules (sister chromatids) attached to each other at a centromere
Define Mutations and DNA repair mechanisms.
DNA repair mechanisms correct mismatches by reversing the synthesis reaction to remove a mismatched nucleotide, then resuming synthesis in the forward direction • When proofreading and repair mechanisms fail, an error becomes a mutation
What is a chromosome number? Define a diploid cell.
Eukaryotic DNA is divided among a number of chromosomes that differ in length and shape • The sum of all chromosomes in a cell of a given type is the chromosome number • Diploid cells have two of each type of chromosome • Each species has a characteristic chromosome number
What is the human chromosome number? How many pairs?Name the two versions are in each pair of chromosomes?
Human body cells have 46 chromosomes (chromosome number 46) • Human body cells have two of each type of chromosome (23 pairs) so the chromosome number is diploid (2n) • Each pair of chromosomes has two versions, one maternal and one paternal
1)True or false: A DNA molecule is not always replicated correctly.
TRUE
What is a Karyotype? and what is it used for? Describe a micrograph. True or false. All of human's chromosomes are homologous.
karyotype • Image of an individual's complement of chromosomes arranged by size, length, shape, and centromere location • Cells taken from an individual are treated to make their chromosomes condensed, stained and then viewed under the microscope • A micrograph of a single cell is digitally rearranged so images of chromosomes are lined up by centromere location, and arranged according to size, shape, and length • A karyotype can reveal abnormalities in an individual's complement of chromosomes
Biochemist _____ had also been working on the structure of DNA, using x-ray crystallography to calculate the size, shape, and spacing between any repeating elements of the molecules.
Rosalind Franklin
Name the people who contributed to the discovery of DNA: In the 1800s, _______ found that nuclei contain an acidic substance composed mostly of nitrogen and phosphorus In the 1900s,______ used two strains of Streptococcus pneumoniae in a series of experiments that revealed a clue about inheritance.
Johannes Miescher, Frederick Griffith
What are autosomes?
Members of a pair of sex chromosomes differ among males and females - the differences determine an individual's sex • All others chromosomes are autosomes, which are the same in both females and males • Autosomes of a pair have the same length, shape, and centromere location, and carry the same genes
What is a nucleosome? What is a histone?
Nucleosome: A length of DNA wound around a spool of histone proteins. Histone: Type of protein that structurally organizes eukaryotic chromosomes.
