Week 19: Genotype to Phenotype I Flashcards
phenotype
An organism’s visible, expressed traits
An organism’s phenotype is all of its observable characteristics — which are influenced both by its genotype and by the environment.
how does natural selection work in regards to phenotypes
Natural selection acts by selecting FOR the best phenotypes, and/or AGAINST those that do not succeed in a given environment
Therefore phenotypes must vary in order for natural selection to cause change over time
Where does phenotypic diversity come from
Genetic diversity
where does Genetic diversity come from
Genetic mutation
Horizontal Gene Transfer (Prokaryotes)
Sexual Recombination of Genes (Eukaryotes)
define Mutation
the alteration of the nucleotide sequence of DNA or RNA
what is the only source of novel traits
Mutation
Mutations may be harmful, neutral, or beneficial… most mutations are ……
neutral or harmful
Effects of a mutation depend on:
All the other genes in an organism
The organism’s environment
A beneficial mutation in a gene may increase fitness Which will result in what?
more of the organism’s genes are passed on through
reproduction to the next generation
Mutation is entirely random with regard to where in the genome it occurs. True or False
true
Somatic (Body) mutations
occur in the cells of the body, and cannot be inherited
spread during mitosis, or regular cell division.
Germline (gamete) mutations
occur in gametes (eggs or sperm) and can be potentially passed on to offspring to either harmful, neutral or beneficial effect
Germline mutations occur during meiosis, or cell division to produce the gametes.
what are the different types of point mutations
transition/substitution
transversion/inversion
insertion
deletion
what is “substitution” point mutation
pg.8
one nucleotide in a DNA sequence is replaced by another nucleotide
ex:
AT pair replaced by GC pair
what is “inversion” point mutation
pg.8
the reversal of a segment of DNA within a chromosome
ex:
AT pair replaced by TA pair
what is “insertion point mutation
pg.8
involves the addition of one or more nucleotides into the DNA sequence
ex:
GC pair inserted
what is “deletion” point mutation
the removal or loss of one or more nucleotides from a DNA sequence
ex:
AT pair deleted
question on page 10
insertion
question on page 13
question on page 15
what point mutation is most likely to produce a nonfunctional protein/most harmful
Frameshift mutations = insertions/deletions
Since the genetic code is read in triplets (codons), a frameshift mutation alters the reading frame, leading to changes in all the amino acids that would occur after that
Most mutations have little to no effect on organisms or their offspring, because…
Most mutations occur in somatic cells.
There is redundancy in translation to protein.
Diploid organisms have a second, functional copy of the gene in the corresponding chromosome
detailed explaination: The presence of a second, functional copy of a gene in diploid organisms provides a level of genetic redundancy that can mitigate the effects of certain mutations.
How does sex produce variation
(look at page 19)
- Alleles comes from two different parents
2.Reassortment of homologues
3.Crossing over
genotype
set of genes that an organism carries
An organism’s phenotype is all of its observable characteristics — which are influenced by both …
genotype and environment
Differences in the genotypes can produce different phenotypes. True or False
true
who is Gregor Mendel
often referred to as the “father of modern genetics” for his pioneering work on the inheritance of traits in pea plants
what are the three main principles of Mendel’s Laws of Inheritance
Law of Segregation
Law of Independent Assortment
Law of Dominance
what is the “Law of Segregation”
alleles of a given gene are separated into different gametes
This law explains why offspring inherit one allele from each parent, leading to the variation of traits in subsequent generations.
What does the “R” gene do?
(Molecular Basis of Wrinkled vs. Round Peas)
(Mendel’s Laws of Inheritance)
The “R” gene DNA encodes a Starch Branching Enzyme protein (SBE1)
How does the SBE1 protein lead to round seeds?
It gives rise to highly branched starch (amylopectin)
Highly branched starch in the seeds leads to seeds with low water content. When the seeds dry, they stay round.
question on page 30
What is a dominant allele/trait
the allele that determines the phenotype in a heterozygote
How are Dominant alleles typically expressed
represented by uppercase letters (e.g., “A”)
how are recessive alleles typically expressed
represented by lowercase letters (e.g., “a”)
when is a recessive allele/trait expresed
only expressed in the phenotype when two copies of the allele (homozygous recessive) are present
If a dominant allele is present, it masks the expression of the recessive allele.
what does Homozygous mean
an individual carries two copies of the same version of a gene: ex. RR
what does Heterozygous mean
an individual carries two different versions of the same gene: ex. Rr.
A heterozygote will always display the phenotype of which allele/trait: dominant or recessive
dominant allele
the R. RR and Rr will have the same gene expression, and the same phenotype.
what are alleles
alternative versions or variants of a gene that are found at the same location (locus) on a chromosome.
Each individual inherits two alleles for each gene, one from each parent. These alleles may be identical (homozygous) or different (heterozygous). True or false
true
question on page 34
C
