38. Hereditary material. Chromosomes - composition, submicroscopic and microscopic structure. Flashcards
Histones - proteins with a high proportion of positively charged amino acids which enables them to bind firmly to the DNA double helix. Play a role in gene regulation
Types: H1, H2A, H2B, H3 + H4. Except for H1, they occur in equal numbers.
Histones - proteins with a high proportion of positively charged amino acids which enables them to bind firmly to the DNA double helix. Play a role in gene regulation
Types: H1, H2A, H2B, H3 + H4. Except for H1, they occur in equal numbers.
Chromatin structures:
- consists of segments of nucleosomes condensed to different degrees
- In the DNA segments lying between series of nucleosomes, sequence specific DNA - binding proteins are found which regulate the expression (activity of genes) (H1 Histones)
- chromosomes contain DNA, RNA, histones and Ca2+ ions associated with the DNA
- chromosomes are densely packed in metaphase
Chromatin structures:
- consists of segments of nucleosomes condensed to different degrees
- In the DNA segments lying between series of nucleosomes, sequence specific DNA - binding proteins are found which regulate the expression (activity of genes) (H1 Histones)
- chromosomes contain DNA, RNA, histones and Ca2+ ions associated with the DNA
- chromosomes are densely packed in metaphase
Polythese chromosomes - over sized chromosomes - developed from standard chromosomes - commonly found in salivary glands of drosophila
Polythese chromosomes - over sized chromosomes - developed from standard chromosomes - commonly found in salivary glands of drosophila
DNA in lampbrush chromosomes
- chromatin so densely packed - not directly visible
- an exception is the interphase nuclei of certain cells
- these chromosomes show RNA synthesis and from unusual loops
DNA in lampbrush chromosomes
- chromatin so densely packed - not directly visible
- an exception is the interphase nuclei of certain cells
- these chromosomes show RNA synthesis and from unusual loops
Euchromatin and Heterochromatin:
Heterochromatin - a region in which a few or no active genes lie
Euchromatin - opposite
Euchromatin and Heterochromatin:
Heterochromatin - a region in which a few or no active genes lie
Euchromatin - opposite
Characteristic regions of a chromosomes:
Centromeres and telomeres contain repetitive DNA sequences.
Characteristic regions of a chromosomes:
Centromeres and telomeres contain repetitive DNA sequences.
Types of metaphase chromosomes:
- Submetacentric - short arm (p arm) long arm (q)
- metacentric - short and long arms are the same length
- acrocentric - show a dense appendage called a satellite
- telocentric - have neither a short arm nor a satellite. None of the human chromosomes are telocentric
Types of metaphase chromosomes:
- Submetacentric - short arm (p arm) long arm (q)
- metacentric - short and long arms are the same length
- acrocentric - show a dense appendage called a satellite
- telocentric - have neither a short arm nor a satellite. None of the human chromosomes are telocentric
Centromeres - link sister chromatids
Telomere - Region of repetitive nucleotide sequence
Centromeres - link sister chromatids
Telomere - Region of repetitive nucleotide sequence