Chapter 29 - DNA And Chromosomes Flashcards
1
Q
Nucleic acid
A
- control the operation of cells
- found in the cytoplasm
- DNA and RNA are nucleic acids
2
Q
Deoxyribonucleic acid (DNA)
A
- contained in the chromosome
- each 4 cm long
- DNA is coiled around a protein called histone
3
Q
What are homologous chromosomes ?
A
- two chromosomes that form a pair
- in which genes are arranged along their length
- control identical characteristics like eye colour
4
Q
What are Genes ?
A
A length of DNA which carries genetic code for particular characteristic. It’s the genetic code for making a specific protein
5
Q
What are Allele ?
A
One of the alternative forms of the same gene. It carries different code for the same protein or characteristic
6
Q
Locus (no not the maths locus)
A
- the precise position of a gene in the chromosome
- alleles occupy the same loci
7
Q
Haploid n
A
- a cell that only has unpaired chromosomes
- it’s half of a diploid
- gametes are haploid
8
Q
Diploid 2n
A
- a cell which has homologous pairs
- somatic cells are diploid
- is double the haploid
9
Q
State what is DNA
A
- material of inheritance
- found in chromosomes
10
Q
Structure of a gene
A
- a chromosome is made of many genes
- a gene is the length of DNA
- each gene control one characteristic
11
Q
Structure of DNA
A
- a long molecule which forms a double helix
- made up of subunits called nucleotides
- each nucleotide is made up of 3 chemical groups
- the first group is sugar called deoxyribose sugar
- the second is nitrogenous base
- four nitrogenous bases are : adenine, thymine, guanine and cytosine
- group three is the phosphate part
- between bonds are weak hydrogen bonds ( two bonds between A and T and three bonds between G and C )
12
Q
Replication of DNA
A
- when cell divides by mitosis to form identical daughter cells
- new chromosomes must be formed before division
- DNA molecule makes copies of itself it’s called replication
13
Q
The semi- conservative replication of DNA
A
- DNA molecule unwinds
- it then unzips
- enzyme DNA polymerase is used to unzip
- allows complimentary strand to separate
- exposed base acts as template
- free nucleotides are are activated by extra phosphate
- complimentary pairing occurs
- backbone is formed by sugar-phosphate
14
Q
Importance of DNA replication
A
- provides identical copies of all genetic instructions
- minimize mistakes
- mistakes can lead to mutation
- mutation can lead to cancer
- mutation can contribute to evolution
15
Q
Transcription
A
- DNA in nucleus partly unwinds
- forms template for syntheses of mRNA
- called transcription
- base is transcribed to complementary base sequence of mRNA
- mRNA passes out the nucleus through the nuclear pores and goes to ribosomes
16
Q
Translation
A
- in ribosomes translation occurs
- amino acids are assembled onto the codons of the mRNA
- tRNA brings amino acids to the anticodon on it to the mRNA
- this forms polypeptide with peptide bonds
17
Q
Remember
A
- RNA have urasil (U) instead of thymine
- if anticodon on tRNA is UAC the codon on mRNA is AUG
- for every amino acid there is one or more codons but no codon codes for more than one amino acid
- this means the amino acids will fit into the correct order in the protein
18
Q
What is a chromosome
A
A long thread like structure in nucleus which carry genetic info and is composed of strands of DNA
