DNA, genes & chromosomes

Created by

Lucy

Cards (35)

When are chromosomes visible?
During cell division
What is each chromosome?
Each chromosome is one molecule of DNA
What are histones?
In eukaryotic cells, molecules of DNA are wrapped around proteins called histones.
What are DNA and histones also known as?
Chromatin fibres
What is the purpose of histones?
They make the molecules of DNA more compact so they can be stored easily.
What are supercoiled chromosomes?
Chromatin is coiled up to form supercoiled chromosomes.
Why are supercoiled chromosomes useful?
Because they can be moved around the cell during mitosis.
Can supercoiled chromosomes be seen under a microscope?
Supercoiled chromosomes can be stained and seen under a light microscope.
Why does chromatin remain as supercoiled chromosomes for as little time as possible?
Because supercoiled chromosomes cannot code mRNA.
What are homologous chromosomes?
Chromosomes occur in pairs called homologous chromosomes
What is a homologous pair?
Two pairs of chromosomes that determine the same genetic characteristics
What makes a pair of chromosomes a homologous pair?
They have the same gene at the same loci
Define locus.
the location of a specific gene on a chromosome
What is an allele?
a different version of the same gene
What does haploid refer to?
Refers to cells that contain only a single copy of each chromosome
What does diploid refer to?
Refers to cells in which the nucleus contains two sets of chromosomes
What is a chromosome?
A structure made of protein & DNA by which genetic information is physically passed from one generation to the next.
What is chromatin?
The material that makes up chromosomes. It consists of DNA and the protein histone.
What is a chromatid?
One of the two strands of a chromosome that are joined together by a single centromere prior to cell division
What is the centromere?
Structure that holds two chromatids together.
Describe the structure of DNA inside mitochondria and chloroplasts.
Short, circular & not associated with histones
Other than the nucleus, which eukaryotic organelles contain DNA?
Mitochondria & chloroplasts
What is the difference between introns & exons?
Introns do not code for amino acids, whereas exons do code for amino acids.
Where is DNA stored in eukaryotic and prokaryotic cells?
In eukaryotic cells, DNA is stored in the nucleus. In prokaryotic cells, DNA is free in the cytoplasm.
How is DNA stored in eukaryotic vs prokaryotic cells?
In eukaryotic cells, DNA is stored as chromosomes inside the nucleus, whereas in prokaryotic cells, DNA is free in the cytoplasm and is supercoiled to fit inside the cell.
What is the shape of DNA in eukaryotic cells vs prokaryotic cells?
In eukaryotic cells, DNA is linear, in prokaryotic cells, DNA is circular.
Which has larger DNA: eukaryotic cells or prokaryotic cells?
Eukaryotic cells have larger DNA than prokaryotic cells
Is eukaryotic DNA associated with proteins?
Yes, it is associated with proteins called histones.
Is prokaryotic DNA associated with proteins?
No, prokaryotic DNA is naked (not associated with proteins)
Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule.
Formed by a condensation reaction
Phosphodiester bond forms between phosphate and deoxyribose
Catalysed by DNA polymerase
How is the DNA in a chloroplast/mitochondria different to DNA in the nucleus?
DNA is shorter
Has fewer genes
DNA is circular not linear
Not associated with histones/proteins, unlike nuclear DNA
Introns are absent, unlike in nuclear DNA
Where is a gene located on a DNA molecule?
At the locus
What does the genetic information that each gene carries determine?
The sequence of amino acids during protein synthesis
What is a gene?
A base sequence of DNA that codes for:
The amino acid sequence of a polypeptide
A functional RNA (including ribosomal RNA and tRNAs)
What does a triplet code for?
A specific amino acid