DNA and Chromosomes Flashcards
What’s there differences in dna from a prokaryotic cell and a eukaryotic cell
Prokaryotic cell- dna molecules are shorter, forms circle and are not associated with protein molecule. Therefore don’t have chromosomes
Eukaryotic cell- dna molecules are longer, form a line rather then a circle. And they occur in association with proteins called histones to form structures called chromosomes.
The DNA in mitochondria and chloroplasts in eukaryotic cells are short circular and not associated with proteins
What’s the structure of a chromosome
Centromere in the middle attached to Chromatids
How is a chromosome formed
Dna molecule
Dna combines with histones
Dna-histones complex is coiled
Coils fold to form loops
Loops coil and pack together to form the chromosome
How may chromosomes do humans have
46
How any dna molecules does a chromosome contain
Just one, although it is very long.
This single dna molecule has many genes along its length. Each gene occupies a specific position (locus) on the dna molecule
What are homologous pairs
two chromomosomes that carry the same genes but not necessarily the same alleles of the genes
What’s the diploid number
The total number. In humans it’s 46
How does each cell receive one gene for each characteristic of an organism
During meiosis, the halving of the number of chromosomes is done in a manner which ensures that each daughter cell receives one chromosome from each homologous pair.
How is the diploid state, with paired homologous chromosomes restored
When the haploid cells combine
What is an allele
One of a number of alternative forms of a gene
Each gene exists in 2, occasionally more, different forms. What are each of these forms called
An allele
What alleles do we inherit from parents
One from each of them.
Why do the different alleles have different polypeptides
As each allele has a different base sequence, therefore a different amino acid sequence, so produced a different polypeptide
What happens in terms of alleles if the base sequence of a gene changes ( mutation )
It produces a new allele or that gene and results in different sequence of amino acids being coded for.
This different amino acid sequence will lead do the production of a different polypeptide and hence a different protein
What happens if the different protein cannot function properly in enzymes
It may have a different shape and new shape may not fit the enzymes substrate. Therefore enzyme may not function and this can have serious consequences for the organism
