7A: Genes and Chromosomes Flashcards
What is a genome, and what does it do?
The complete set of DNA in an organism’s haploid cells. In humans, almost every cell in the body contains a complete copy of the genome. The genome contains all of the information needed for development, function and reproduction.
What is a gene?
A section of DNA that codes for a protein
What is an allele?
The variations of a gene
A particular form of a gene with a unique nucleotide sequence.
General trend in genome size and gene number in different cells?
Prokaryotes/viruses: 1 allele because of asexual reproduction (and identical daughter cells)
Eukaryotes: 2 alleles
Gene number also same.
Why is the number of chromosomes in an organism not a reflection of their genetic complexity?
Genetic complexity is the number and organization of genes within its genome, not the number of chromosomes
Plants have more chromosomes than more complex organisms (gorillas)
What is a nucleotide made of?
Phosphate group
Deoxyribose sugar
Nitrogenous base (adenine + thymine, guanine + cytosine)
Organization of chromosomes from biggest to smallest?
Cell -> Nucleus -> Chromosome -> Chromatin -> Nucleosomes -> Histone -> DNA -> Base pairs
What is a histone?
A protein that DNA coils around
What is a nucleosome?
DNA coils are further coiled into super coils called nucleosomes
Two types of macromolecules in chromosomes?
Nucleic acid and proteins (histone)
What is DNA?
Polymer inside a nucleus with the genetic information responsible for the development and function of an organism
What is aneuploidy?
Occurs in organisms which has an extra or missing chromosome (caused by non-dysjunction)
When an organism is missing 1 chromosome, is it called ___?
Monosomy
When an organism has 1 extra chromosome, is it called ___?
Trisonomy
When an organism has 2 extra chromosomes, is it called ___?
Tetrasomy
When an organism has an extra set of chromosomes (3 in each set), is it called ___?
Polyploidy
How are karyotypes made?
Chromosomes are condensed and stained, and matched together. This occurs in metaphase.
What is down syndrome?
Trisomy 21 - 3 chromosomes in the set
What is Klinefelter syndrome?
When a male has an extra X chromosome (XXY)
What is Turners syndrome?
When one X chromosome in a female is missing/partly deleted (XO)
Does each gene always have exactly two alleles?
No, for example, the ABO blood type system (there are three)
Are all genes made of the same nucleic acid monomers?
Yes, DNA and RNA which are made of the same monomers (A,C,G,T)
What information is coded into DNA?
The instructions for all the proteins the organism will ever synthesize
What does 3’ and 5’ mean?
Refers to the number of carbon atoms in a deoxyribose sugar molecule that a phosphate group binds to.
Describe the general trend for genome size and gene number for viruses, bacteria, and eukaryotic organisms
Virus (small genome size, few number of genes) -> prokaryote (medium genome size and number of genes) -> eukaryote (large genome size, large number of genes)
What is chromatin?
A complex of DNA and protein
What is a chromatid?
One half of a replicated chromosome
Differences between sex chromosomes and autosomes?
Autosomal genes determine most phenotypic characteristics, whereas sex chromosomes determine the biological sex
Where is the same form of a gene found?
Sister chromatids
