dna, genes and chromosomes Flashcards
What are the 3 components of nucleotides
- Pentose sugar
- Phosphate group
- Organic base
Describe the structure of DNA
- Deoxyribose sugar
- Phosphate group
- One of four organic bases (A, T, C, G)
- Double-stranded
- Hydrogen bonds between bases form a helix shape
Describe the role of DNA
Carries genetic information, determines our inherited characteristics
Describe the structure of RNA
- Ribose sugar
- A phosphate group
- 1 of four organic bases (A, U, C, G)
- Single-stranded
Describe the role of RNA
Transfers genetic information from DNA to ribosomes for protein synthesis
Which bases are purine and which are pyrimidine?
Purine (2x ring) = adenine, guanine
Pyrimidine (1x ring) = cytosine, thymine, uracil
How is DNA in eukaryotic cells different from in prokaryotic cells?
- Eukaryotic DNA is found in the nucleus and is long and linear, associated with histone proteins to form chromosomes
- Prokaryotic cells are short and circular, not associated with histone proteins
What is the genetic code?
The order of bases on DNA, consists of codons
Define codons
Triplets of bases that code for a particular amino acid
Identify features of the genetic code
- Non-overlapping so each triplet is only read once
- Degenerate so more than one triplet code for the same amino acid
- Universal because the same bases and sequences are used by all species
Define a gene
A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids to make a polypeptide can also code for functional RNA
Define locus
The fixed position on a DNA molecule occupied by a gene
Define an allele
Different versions of the same gene found at the same locus on a chromosome
What are exons?
Exons are sections of a gene that do code for an amino acid
What are introns?
Introns are sections of DNA that don’t code for amino acids
Where are introns found?
- Between exons
- Within genes
Describe the DNA in the mitochondria and chloroplast
- It’s circular and shorter than DNA molecules in the nucleus
- It isn’t associated with histone proteins
Describe nuclear eukaryotic DNA
- Eukaryotic cells contain linear DNA molecules that exist as chromosomes
- DNA molecule is long
- DNA molecule is wound around proteins called histones
- HIstone proteins support the DNA
- The DNA is coiled tightly to make a compact chromosome
What occurs to introns
Introns are removed during protein synthesis so they don’t affect the amino acid order
Describe non-coding repeats
- Eukaryotic DNA contains regions of multiple repeats outside of genes
- These areas don’t code for amino acids
What determines the order of amino acids in a polypeptide
The order of amino acids in a polypeptide is decided by the order of bases in a gene
How is an amino acid coded for
Each amino acid is coded for by a sequence of 3 bases in a gene called a triplet
What do genes that don’t code for a polypeptide code for instead?
Genes that don’t code for a polypeptide code for functional RNA
Define the genome
A cell’s genome is a complete set of genes in the cell
Define the proteome
A proteome is the full range of proteins that the cell is able to produce
How do alleles code for different versions of the same polypeptide?
- The order of bases in each allele is different
- So they code for different versions of the same polypeptide
How many chromosomes do humans have
23 pairs
What are homologous pairs?
Homologous pairs are pairs of matching chromosomes
Where are alleles coding for the same characteristics found?
They are found at the same fixed position on each chromosome in a homologous pair
