AP BIOLOGY

HEREDITY

MUTATIONS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Chromosomes are
A
Tightly wound strands of DNA
B
Tightly wound proteins
C
Found in the mitochondria
D
Not important for cell division
Explanation: 

Detailed explanation-1: -In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.

Detailed explanation-2: -Figure 1: Chromosomes are composed of DNA tightly-wound around histones. Chromosomal DNA is packaged inside microscopic nuclei with the help of histones. These are positively-charged proteins that strongly adhere to negatively-charged DNA and form complexes called nucleosomes.

Detailed explanation-3: -Condensed DNA is found in a tightly packed area of chromatin called heterochromatin. Its transcription is dormant. The transcriptionally active portion of chromatin is called euchromatin, which is loosely packed.

Detailed explanation-4: -Condensing DNA into chromosomes prevents DNA tangling and damage during cell division.

Detailed explanation-5: -Figure 5: To better fit within the cell, long pieces of double-stranded DNA are tightly packed into structures called chromosomes.

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