Presentation is loading. Please wait.

Presentation is loading. Please wait.

DNA Structure and Function

Similar presentations

Presentation on theme: "DNA Structure and Function"— Presentation transcript:

1 DNA Structure and Function
Basis of Heredity

2 Chemical Basis of Life

3 The Central Dogma cells can make exact copies of DNA
replication transcription processing translation cells can make exact copies of DNA DNA encodes all of the information necessary for cellular functions RNA is made from a DNA template and functions in protein synthesis proteins are translated from messenger RNA and carry out cellular functions

4 Nucleotides nucleotides are the building blocks of nucleic acids ribose + base + 5' phosphate 5 different bases adenine (A) guanine (G) cytosine (C) thymine (T) uracil (U) DNA vs RNA 2' oxygen thymine (T) uracil (U) double stranded single stranded DNA = deoxyribonucleic acid RNA = ribonucleic acid

5 Nucleic Acid Structure
nucleic acids are polymers of nucleotides nucleotides linked through phosphate bonds strand has polarity—5'-PO4 and 3'-OH ends order of the nucleotides defines a sequence 4 letter alphabet

6 Double Strands specific base pairing A and T G and C hydrogen bonds
anti-parallel (5'-3') complementary strands template for synthesis

7 DNA Replication the DNA strands are separated
each strand serves as template complementary strands are synthesized (5'3') yields 2 identical DNA molecules semi-conservative replication carried out by cellular proteins (= enzymes) complex process involving many proteins DNA polymerase

8 DNA Polymerase Activity
'replication fork' moves along DNA leading strand lagging strand numerous replication forks act simultaneously

9 Chromosomes genomic DNA is very long humans, 6 x 109 bp
~1.8 meters total length total length reduced via associates with proteins individual DNA molecules condensed into chromosomes humans have 22 pairs + X/X or X/Y (ie, diploid)

10 Chromosome Replication
unfolding of chromosomes, DNA replication, and refolding chromosomal duplication sister chromatids joined at centromeres

11 Mitosis DNA synthesis chromosomal duplication
separation of sister chromatids cell division (cytokinesis) results in 2 identical daughter cells somatic cell reproduction asexual process sexual reproduction involves germ line cells oogenesis (egg formation) spermatogenesis (sperm formation

12 Meiosis two consecutive rounds of cell division meiosis I
DNA replication (2n4n) separation of chromosome pairs (4n2n) meiosis II no DNA replication separation of chromatids (2n1n) fertilization (1n2n)


14 Recombination independent chromosome assortment 2n possible variants
'crossing-over' recombination between homologous chromosomes at least once per chromosome pair positions ~ random

15 Genes and Alleles gene = unit of information (~protein)
locus = physical location on a chromosome allele = different molecular forms (ie, sequence) of a gene homozygous = same allele on both chromosomes heterozygous = different alleles on chromosome pairs genotype = genetic makeup (ie, total genes) phenotype = observable traits

16 Types of Inheritance dominant-recessive
dominant allele 'masks' recessive allele incomplete dominance phenotype between dominant and recessive traits co-dominance shared expression of traits (eg, AB blood type) polygenic several genes influence trait (often continuous variation) pleiotrophy single gene affecting several traits

Download ppt "DNA Structure and Function"

Similar presentations

Ads by Google