Please enable JavaScript.
Coggle requires JavaScript to display documents.
Biology Ch 16 (Chromosomes (Chromosomes in DNA (In the nucleus of each…
Biology Ch 16
Chromosomes
A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
Telomeres
Eukaaryotes have repetetive, non coding sequences called telomeres at the ends of their DNAs.
-
Chromosomes in DNA
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.
-
-
"painting chromosomes"
Researchers can treat human chromosomes with molecular tags that cause each chromosome pair to appear a different color,
Chromosome painting is a term used to describe the direct visualisation using in situ hybridisation of specific chromosomes in metaphase spreads and in interphase nuclei.
Reverse chromosome painting is able to identify not only the chromosomal origin of marker chromosomes but also the regions and breakpoints involved.
Heterochromatin
chromosome material of different density from normal (usually greater), in which the activity of the genes is modified or suppressed.
Enchromatin
chromosome material which does not stain strongly except during cell division. It represents the major genes and is involved in transcription.
Chromatin
-
The material of which the chromosomes of organisms other than bacteria are composed. It consists of protein, RNA, and DNA.
DNA
DNA is made up of molecules called nucleotides. Each nucleotide contains a phosphate group, a sugar group and a nitrogen base. The four types of nitrogen bases are adenine, thymine, guanine, and cytosine. To fit inside cells, DNA is coiled tightly to form structures we call chromosomes.
-
-
Steps of DNA replication
There are three main steps to DNA replication: initiation, elongation, and termination. In order to fit within a cell's nucleus, DNA is packed into tightly coiled structures called chromatin, which loosens prior to replication, allowing the cell replication machinery to access the DNA strands.
DNA mutation types
Base substitutions
They are the simplest type of gene-level mutation, and they involve the swapping of one nucleotide for another during DNA replication.
For example, during replication, a thymine nucleotide might be inserted in place of a guanine nucleotide.
Deletions
A deletion is a mutation in which a part of a chromosome or a sequence of DNA is left out during DNA replication. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome.
-
Insertions
When by accident extra DNA bases are added to the DNA. ... Insertion mutations cause the production of the wrong amino acids, cause early termination of the amino acid chain ( protein), and change highly structured information stored in the DNA to nonsense producing non functional proteins.
-
Figures
Figure 16.14
Addition of a nucleotide to a DNA strand. DNA polymerase catalyzes the addition of a nucleotide to the 3'' end of a growing DNA strand, with the release of two phosphates.
-
Figure 16.15
Synthesis of the leading strand during DNA replication. This diagram focuses on the left replication fork shown in the overview box. DNA polymerase lll shaped like a cupped hand, is shown closely associated with a protein called the "sliding clamped" that encircles the newly synthesized double helix like doughnut. the sliding clamp moves DNA pol lll along the DNA template strand.
-
Figure 16.16
Synthesis of the lagging strand.a primase "reads" the template DNA and initiates synthesis of a short complementary RNA primer. The RNA primers are then removed and replaced with DNA, and the fragments of DNA are joined together by DNA ligase.
-
Figure 16.17
A summary of bacterial DNA replication. The detailed diagram shows the left-handed replication fork of the replication bubble shown in the overview. Viewing each daughter strand in its entirety in the overview, you can see that half of it is made continuously as the leading strand, while the other half is synthesized in fragments as the lagging strand.
-
