Genetics - Week 1 Flashcards
How many chromosomes are in the human genome?
- 23 different types of chromosomes
- diploid cells have two of each type (2n)
there are 46 total chromosomes
How do different types of chromosomes differ?
- size
- shape
- location of centromeres
- genes
What is an unreplicated chromosome?
each chromosome contains one double-stranded DNA molecule and one centromere
What is a centromere?
specialized region of DNA that links sister chromatids, and also allows for proteins to bind during mitosis/meiosis
What is a replicated chromosome?
each chromosome contains two identical double-stranded DNA molecules, aka two sister chromatids
How many centromeres are on each chromosome?
whether replicated or unreplicated, each chromosome has only one centromere
of centromeres = # of chromosomes
When is DNA tightly coiled and bunched?
when chromosomes are in their condensed form
What are sister chromatids?
two identical double-stranded DNA molecules
- have identical sequences
What are alleles?
genetic variants of genes
What is a chromosome?
condensed DNA + proteins
What is a chromatid?
one uninterrupted DNA molecule + associated proteins
- used to describe chromosomes only when there are 2 DNA molecules (sister chromatids)
- however you can think of a single chromatids as a single DNA molecule
What is a haploid (n) cell?
has one of each type of chromosome
of chromosomes = n
What is a diploid (2n) cell?
has two of each type of chromosome
of chromosomes = 2n
How many chromosomes do we usually see in species with polyploidy?
even numbers of chromosomes
What is polyploidy?
more than two copies of each chromosome
What is a karyotype?
picture of an individual’s chromosomes
Describe how ploidy level varies between species.
- many organisms (ie. mushroom, yeast) take a haploid form during all or part of their life cycle
- in some cases, the extra sets of chromosomes can make the organism more robust than it would be otherwise
- an odd number of chromosomes, however, often leads to sterility and abnormalities
What is a genome?
all of the DNA in a cell
Describe the female and male genomes.
- females have a bigger diploid genome than males in humans
- females have X chromosomes
- males have Y chromosomes
What is the genome of the plant cell?
nuclear + mitochondrial + chloroplast genomes
What is the genome of the animal cell?
nuclear + mitochondrial genome
What is the genome of the prokaryotic cell?
genome (in nucleoid)
What is the mitochondrial genome?
- human mitochondrial genome is distinctly different from that of the nuclear genome
- contained in a single, circular chromosome (similar to most bacteria)
- in humans (and most other species), mitochondria are normally inherited exclusively from the mother
- variable in size
What is the chloroplast genome?
- photosynthetic organisms (ie. plants, algae, cyanobacteria) will have an additional distinct genome called the chloroplast genome
- circular in nature (similar to most bacteria)
