Chapter 5 Flashcards
What is the maternal affect
Inheritance pattern where the genotype of the mother directly determines the phenotype of her offspring
What is a general explanation of how maternal affect is possible
Maturing oocytes are surrounded by maternal cells that provide them with nutrients
The nurse cells are diploid whereas as the oocytes become haploid
Is a mother is heterozygous then the haploid oocyte can develop either the dominant or recessive gene
During maternal affect what happens if the sperm fertilizing the egg has a Dominant allele
It is irrelevant because the expression of the sperm will be too late to change early embryonic development
What kind of role does maternal effect genes play in early steps of embryosis
Cell division, cleavage pattern
Accumulation of maternal effect gene products before fertilization allows early steps of embryogenesis to pursue very quickly
What is epigenetic inheritance
Modification occurs to the nuclear gene or chromosome that alters gene expression
Does epigenetic inheritance change the DNA sequence
No and it’s reversible
Expression is not permanently changed over the course of multiple generations
What is the purpose of dosage compensation
Offset differences in the number of active sex chromosomes
What is a Barr body
Highly condensed structures in interphase nuclei of somatic cells (highly condensed X chromosome)
How does dosage compensation occur in mammals
Inactivation of a single X chromosome is females
Chromosome condensation
When does X chromosome inactivation occur
In early development
DNA becomes highly compacted and most genes on the inactivated X cannot be expressed
What happens when the inactivated X chromosome is replicated during cell division
Both copies remain highly compacted and inactive
It is passed on to all future somatic cells
In mammalian cells how many X chromosomes remain active
One
Additional X chromosomes are converted to Barr bodies
What does X chromosome inactivation in mammals depend on
The X inactivation center and Xist
What is Xist
A gene that makes a gene product
What is Xic
A short region on the X chromosome that is termed the X inactivation center
Each X chromosome must have an Xic region for inactivation to occur
What is genomic imprinting
When a Segment of DNA is marked and the effect is maintained throughout the life of the organism inheriting the marked dna
Depending on how the genes are marked depends on if the offspring expresses the maternal and paternal inherited allele but not both
What is monoallelic expression
When a gene is marked and expressed either maternal or paternal inherited alleles but not both
What can genetic imprinting involve
Single gene
Part of a chromosome
An entire chromosome
All chromosomes of a single parent
If genomic imprinting must involve a marking process what is involved
An imprinting control region located near the imprinted gene
It is methylated in either the oocyte or sperm but not both
What does the ICR contain
Binding sites for one or more transcription factors that regulate imprinted genes
For most genes methylation causes inhibition or transcription
In regards to methylation what does each parent inherit and how is this maintained
Each parent inherits a methylated and unmethylated gene which is maintained in somatic cells
When is methylation removed
In gamete forming cells
What is extranuclear inheritance
Inheritance patterns that involve genetic material outside of the nucleus
Also considered cytoplasmic inheritance
Involves the mitochondria and cytoplasm
Where is genetic material in mitochondria and chloroplast located
Nucleoid
What is genome made of
Single circular chromosome containing double stranded dna
Do chloroplasts or mitochondria tend to have more nucleotides per organelle
Chloroplast
Organelles contain more than one nucleotide (by the way)
What is the function of the mitochondria
Oxidative phosphorylation
What is a heterogamous species
They produce two kinds of gametes
Female gametes are large and male gametes are small
Species with maternal inheritance may sometimes exhibit what
Paternal leakage
Paternal parent occasionally provides mitochondria through sperm
