Chapter 6:DNA structure and replication Flashcards
What does DNA stand for?
Deoxyribonucleic Acid
What is a gene?
Genetic material is carried and stored in coded in genes, one section of DNA and can be switched off on and by other genes
What does expressed mean?
A gene switched on
Where is DNA found in Eukaryotes?
Nucleus, chloroplasts and mitochondria
What is chromatin?
DNA in a non-dividing cell which only appears grainy and undefined under a microscope
What happens to chromatin when a cell prepares to divide?
Condenses by coiling up and thickens allowing individual chromosomes to be seen
What is a chromosome?
One molecule of DNA with its associated proteins
How is DNA displayed?
Double stranded molecule
What is an unduplicated chromosome?
A long double helix molecule coiled around a histone protein
What is a histone?
A protein that DNA winds around in eukaryotic cells
What are sister chromatids?
Two identical copies of a single chromosomes, formed by replication and connected by centromere
What is a centromere?
A waist like construction in a chromosome required for the movement of chromosomes during cell division
What shape do sister chromatids and centromeres form?
X shape
When are chromosomes visible?
Prior to division stage and after replication has occurred
What are homologous chromosomes?
pair of chromosomes that have the same size, shape and genes at the same location
Where do the chromosomes come from in homologous chromosomes pairs?
One is inherited from each parent
What is karyotype?
The display of the number and appearance of the chromosomes of organisms or observed in metaphase
How many pairs of chromosomes do humans have?
23 pairs (46 chromosomes)
What is the endosymbiotic theory?
A theory that suggests chloroplast and mitochondria arose from ancient prokaryote cells that were ingested by other prokaryote host cells
What is maternal inheritance?
Inheritance only from mothers; any trait that is encoded by organelle DNA only from mother
What is a nucleoid?
The region within a prokaryotic cell that contains the genetic material.
Where are chromosomes join in prokaryotic cells?
A single circular chromosome which lies within the cytoplasm. Chromosomes often join to plasma membrane.
What is plasmid?
A small circular piece of DNA found in bacteria which can replicate independently of the cell’s chromosomes
What is a nucleotide?
The basic building block of nucleic acids linked by phosphodiester bonds
What are nucleotides made of?
five-carbon sugar, a phosphate group and nitrogenous base.
What are the 4 kinds of nitrogenous bases in DNA?
Adenine, thymine, guanine and cytosine
What is complementary bases?
The nitrogenous bases on nucleotide that bind to each other
What are complementary bases that bind?
A to T and C to G
What holds the double helix together?
Hydrogen bonds
What does antiparrell mean and do double helix have it?
Yes, it means they run the opposite ways
How is RNA different to DNA?
RNA is a single strand chain of nucleotides, thymine is replaced by base uracil and ribs sugar replaces deoxyribose of DNA
How is RNA useful?
It is useful in protein synthesis
Why does DNA replicate?
Growth, repairs and reproduction
What is a daughter cell?
Either of the two cells formed during cell division
What is the start of cell division?
The enzyme helicase which helps the double helix unwind by breaking the hydrogen bonds and separate
How does Helicase unwind and separate the strands?
By breaking the hydrogen bonds exposing the nucleotide bases
What is parental DNA?
The DNA of the original cell
What happens during interphase?
Active growth, synthesis of DNA and preparation of next division
What is a replication fork?
The junction between unwound DNA and joined DNA
What is DNA polymerase?
An enzyme capable of making exact copies of DNA fragments
What happens after hydrogen bonds are broken?
DNA polymerase attaches the appropriate base pair to expose nucleotide running in a 3 prime to 5 prime
What is semiconservative replication?
A double helix consisting of a parental strand and daughter stand. Is the outcome during cell division
