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)
What is the nuclear genome?
- composed of linear DNA molecules
- in humans, these are organized as 46 linear chromosomes inherited from two parents
What is a gene?
specific region of a chromosome which encodes (contains the DNA sequence information for making) a functional RNA molecule or protein molecule
What is transcription?
DNA to RNA
What is translation?
RNA to protein
Describe the relationship between number of genes and genome size.
number of genes in a genome cannot be predicted based on genome size
Describe the differences in different genomes.
- can vary widely in the proportion of genes to non-coding DNA
- can be tightly packed or widely dispersed
Describe the relationship between complexity (# of cells) and genome size.
complexity (# of cells) of the organism does not correlate to its genome size
