BIOL 121 Flashcards
What is DNA?
DNA is a double stranded molecule shaped like a spiral ladder
What are genes?
Genes are small sections of DNA that code for a specific protein
What does the Human Genome Project estimate?
- humans have 20-25k protein coding genes
- ranges in size from a few hundred to over 2 million
What is a phenotype?
- observable physical properties of an organism
- physiological, morphological, behavioural
What are alleles? What are they responsible for?
- Alleles are different versions of the same genes
- they are responsible for variation in inherited traits
Alleles rise due to what?
Mutations in the DNA
What is a mutation?
A change in the sequence of nucleotides in the DNA
A mutation may be as small as …
a change in one nucleotide/step
Types of mutation include:
- substitution
- insertion
- deletion
How can mutation be caused?
- due to mistakes when DNA is replicating
- environmental factors that damage DNA (UV)
Explain why white black bears exist
- single nucleotide substitution of Adenine for Guanine in the mc1r gene
- protein produced by this new allele was non-functional
- resulted in white instead of black fur
What is sickle cell disease caused by?
A SNiP in the beta-globin gene
Explain the sickle cell disease (mutation and outcome)
- 6th amino acid is valine instead of glutamic acid, affecting the shape (function) of Hb
- results in red blood cells turning sickle-shaped
- negative effects on oxygen carrying capacity
What is DNA packaged into?
Chromosomes
Where are chromosomes located in?
- nucleus of somatic cells
- gametes
What are somatic cells? Give examples.
- all cells int he body that aren’t sperm and egg cells
- examples include cells of internal organs, skin, bones, blood, connective tissue …
What are gametes? How are they produced?
- reproductive cells produced by sexually reproducing organisms
- produced via meiosis
How many chromosomes are in a human somatic cell?
- typically 46 total chromosomes
Human somatic cells typically have how many pairs of chromosomes?
- 23 total pairs
- 22 pairs of autosomes
- 1 pair of sex chromosomes
Why do you have 23 pairs of chromosomes?
- you inherit one set of 23 chromosomes from your mom
- you inherit one set of 23 chromosomes from your dad
- in total you have 46 chromosomes OR 23 pairs
What are homologous chromosomes?
Homologous chromosomes are a matched pair of chromosomes
What do homologs have in common? Differ?
- they are the same size and have the exact same centromere location
- they carry the same sequence of genes
- may carry different alleles
What is a centromere?
- the constriction point on a chromosome, which divides into two arms
What is a locus?
A specific location on a specific chromosome
What is a ploidy?
The number of each type of chromosome present
(number of copies of each chromosome type)
What is a haploid, diploid, and polypoid?
- haploid =1 of each type of chromosome
- diploid = 2 of each type of chromosome
- polypoid = 3 or more of each type of chromosome
What is the haploid number for our cells?
2n=46
n=23
Polyploidy is common in what?
Common in plants
What does the term genome mean?
It refers to the entire set of DNA instructions found in a cell
Why is the genome important?
It provides all the information that an organism requires to function
What is unreplicated chromosome?
Explain the term “replicated chromosome” in terms of sister chromatids
- replicated DNA consists of 2 identical chromatids
- the 2 sister chromatids should carry the same allele
Define chromatid
One DNA molecule
What is a homozygous genotype?
same alleles of a gene (BB or bb)
What is a heterozygous genotype?
different alleles of a gene (Bb)
