DNA and Chromosomes Flashcards Preview

Biology-8-DNA, Genes and Protein Synthesis > DNA and Chromosomes > Flashcards

Flashcards in DNA and Chromosomes Deck (16):

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



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


State the function of the protein found in chromosomes

It fixes the dna into position