Chromosomes and Genes

Flashcards about Chromosomes and Genes

What is a chromosome?

Thread-like structure made of chromatin (DNA tightly coiled around histones).

Why do cells package their DNA?

To protect DNA and regulate which genes are accessed and when.

How is DNA compacted to fit within cells?

DNA is complexed with histones to form nucleosomes, which fold up to produce a 30-nm fiber, compressed into a 250-nm-wide fiber, and then tightly coiled into the chromatid.

What is chromatin?

A fiber made of DNA tightly coiled around structural proteins called histones.

What is a karyotype?

A map or image of all the chromosomes in a cell, arranged in pairs based on size and structure.

What are telomeres?

Protective molecular caps located at the ends of chromosomes.

How many chromosomes do human somatic cells have?

46 (23 pairs)

What are non-dividing cells?

Cells in normal operation, with chromatin loosely coiled to allow gene access.

What are dividing cells?

Cells in the process of dividing, with chromatin tightly coiled to form the chromosome shape.

What are Somatic Cells?

Cells (except gametes)

What are gametes?

Sex cells

What does diploid(2n) mean?

Meaning that most of their chromosomes come in matched sets known as homologous pairs

What does haploid(n) mean?

Meaning that they only have one of each pair of chromosomes

What is a gene?

A sequence of DNA pairs that codes for a particular purpose, mostly the production of proteins.

What are alleles?

Different versions of a gene.

What are homologous chromosomes?

A pair of chromosomes that contain the same genes but not necessarily the same alleles