Cells and DNA Flashcards
BLENDING INHERITANCE
Darwin’s idea that offspring would be an “average” of their parents (not correct)
ISSUE WITH BLENDING INHERITANCE
- cannot explain how variation persists across generations
- dilutes and eventually eliminates variation
- traits would continuously blend and average out, eventually leading to a population with uniform characteristics, making natural selection impossible
THE CELL
Basic unit of life (comprised of genetic material)
PROKARYOTIC CELLS
Single-celled organisms without a nucleus.
EUKRAYOTIC CELLS
Complex cells with a nucleus and organelles.
CHROMOSONES
- Small linear bodies contained in every cell
- Replicated during cell division
- Exist in homologous pairs in diploid organisms
CELL DIVISON: MITOSIS
The division of cells in which two exact copies of chromosome pairs are made (diploid)
CELL DIVISON: MEIOSIS
Cell division creating haploid gametes for reproduction
FERTILIZATION
The process in which haploid sperm join haploid ovum to produce a zygote. (zygote is diploid)
DNA
- Double helix of nucleotides with phosphate-sugar backbone
- Stores information
- The chemical basis of hereditary
- Responsible for the genetic makeup of an individual
- Adenine (A) only bonds with Thymine (T)
- Cytosine (C) only bonds with Guanine (G)
- “Alphabet” with four repeating letters in infinite combinations
DIFFERENCES IN DNA SEQUENCE LEAD TO VARTIATION THROUGH TWO WAYS:
1) Some DNA codes for proteins
2) Some DNA codes for regulatory sequences
GENE
- Segment of DNA that makes a functional product
- Unit of hereditary, specifies traits
- Arranged on chromosomes “like beads on a string”
- Each gene found at a specific point on the chromosome (locus)
- Segregates as a unit during gamete formation
PROTEIN-CODING GENES
DNA sequences code for two main types of protein:
- Enzymes
- Non-enzymatic proteins
ENZYMES
Proteins that catalyze chemical reactions in cells
EXONS
- Coding sequences in genes, spliced together
- Covalently bonded to one another to create mature mRNA
INTRONS
- Non-coding sequences removed during RNA processing
- Intros are removed by RNA splicing as RNA matures, meaning that they are not expressed in the final messenger RNA (mRNA)
REGULATAORY SEQUNCES
DNA segments controlling gene expression timing
MUTATIONS
- Changes in DNA sequence
- Can cause a change in chromosome # / structure
- Not always negative, source of variation
POINT MUTATION
Change in a single DNA base
RECOMBINATIONS
- New combinations of alleles
- Created through the breaking and rejoining of DNA strands in a new order
- Source of variation
HOMOZYGOUS
The individual carries two identical alleles for a given gene
HETEROZYGOUS
The individual carries two different alleles for a given gene
DOMINANT TRAIT
An allele that suppresses other alleles
RECESSIVE TRAIT
An allele whose expression is suppressed by dominant forms
No effect on phenotypes in heterozygotes
GENOTYPE
Refers to the particular combination of genes or alleles that an individual carries (e.g. AA, Aa, aa)
PHENOTYPE
Refers to the observable characteristics of the organism, such as the colour of the peas in Mendel’s experiments
