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63 Cards in this Set

  • Front
  • Back
Selective gene expression during development results in _____.
_____ is a multistep process in which abnormally growing and dividing cells disrupt body tissues.
_______ ______ govern the kinds and amounts of substances that are present in a cell at any given time.
Gene controls
Each cell rarely uses more than ___ percent of its genes at one time
The process by which cells of a multicelled organism become specialized
_______ occurs as different cell lineages begin to express different subsets of their genes during development
Gene controls
The “switches” that turn gene expression on or off
Molecules or structures that start, enhance, slow, or stop the individual steps of gene expression
Gene controls
Gene control points
Transcription factor
Regulatory protein that influences transcription; e.g., an activator or repressor.
Regulatory protein that blocks transcription.
Regulatory protein that increases the rate of transcription when it binds to a promoter or enhancer.
Binding site in DNA for proteins that enhance the rate of transcription.
Cascades of ______ ______ govern the development of a complex, multicelled body.
gene expression
Master gene
Gene encoding a product that affects the expression of many other genes.
______ ______ encode products that affect the expression of many other genes.
Master genes
Pattern formation
Process by which a complex body forms from local processes during embryonic development.
Homeotic genes
Type of master gene; its expression controls formation of specific body parts during development.
All _____ _______ encode transcription factors with a homeodomain, which is a region of about sixty amino acids that can bind to a promoter or some other sequence of nucleotides in a chromosome.
homeotic genes
Knockout experiment
An experiment in which a gene is deliberately inactivated in a living organism.
How do genes control development?
Development is orchestrated by cascades of master gene expression in embryos.

The expression of homeotic genes during development governs the formation of specific body parts. Homeotic genes that function in similar ways across taxa are evidence of shared ancestry.
____ ____ ____ gives rise to many traits.
Selective gene control
X chromosome inactivation
Shutdown of one of the two X chromosomes in the cells of female mammals.
Dosage compensation
Theory that X chromosome inactivation equalizes gene expression between males and females.
The master gene for male sex determination in mammals
Differences in cell types are not due to different genes being present but due to __________ which is the expression of different genes by the cells with the same genome.
The control of gene expression contributes to two important properties of the cell, which are:
1. Cells respond to changes in the internal and external environment by turning genes on and off.
2. The cells of multicellular organism become highly specialized with very specific structure and function.
Points of control over gene experssion
Control consist of processes that start, enhance, slow or stop gene expression. These controls are
1. Controls of Transcription
2. mRNA Processing
3. mRNA transport
4. Translational control
5. Post translational modification.
2 types of transcription factors
Activators, Repressors
Chemical modifications in gene expression
Chemical modifications of DNA affect RNA polymerase’s access to genes
Attachment of methyl groups to the cytosine causes DNA to wind tightly around histones preventing transcription.
Acetyl groups are attached to the lysine in histone tails and prevents them from binding to the neighboring nucleosomes, thus promoting transcription.
Alternative splicing (in mRNA processing)
Different mRNA molecules are produced from the same primary transcript depending on which exon are spliced out.
mRNA localization
Delivery within cytoplasm (mRNA localization) – A short base sequence near an mRNA’s Poly A tail is like a ZIP CODE.
Proteins attach to the zip code and drag the mRNA to the particular organelle or area of cytoplasm.
Prevents the RNA from being translated before it reaches its destination.
Controls over mRNA stability (translational controls)
The life span of mRNA molecules in the cytoplasm is important in determining the pattern of protein synthesis in a cell.
RNA INTERFERENCE (translational control)
miRNA are short segments of RNA molecules that bind to the mRNA and prevents mRNA from being translated a process called as RNA INTERFERANCE. So expression of miRNA complementary in sequence to a gene inhibits expression of that gene.
In eukaryotic cells transcriptional control can operated on at least 3 levels, which are
The individual gene
Regions of chromosome
Entire chromosome.
The theory that X chromosome inactivation equalizes expression of X chromosome genes between the sexes
Dosage compensation
Mechanism of X inactivation
XIST gene on one X chromosome transcribes an RNA molecule which coats the chromosome and causes it to condense, forming a Barr body
X Chromosome inactivation
In cells of female mammals, either the maternal or paternal X chromosome is randomly condensed (Barr body) and is inactive
Occurs in an early embryonic stage, so that all descendants of that particular cell have the same inactive X chromosome, resulting in “mosaic” gene expression.
The ABC model (flower formation)
Three sets of master genes (A,B,C) encode products that initiate cascades of expression of other genes to accomplish intricate tasks such as flower formation
Master genes are expressed differently in tissues of floral shoots
Master genes are switched on by environmental cues such as day length
Prokaryotes are single celled and do not have ____ ______
master genes
Prokaryotes control gene expression mainly by adjusting the______ in response to shifts in _______ and other outside conditions
rate of transcription; nutrient availability
In ______, genes that are used together often occur together on chromosomes
An operon consists of 4 parts, which are
A regulatory gene: Which controls the timing or rate of transcription of other genes
A promoter: RNA polymerase binding site
An operator: A binding site for repressor
Structural genes: Genes that encode the enzymes required for lactose breakdown.
the lac operon
E. coli digest lactose in guts of mammals using a set of three enzymes controlled by two operators and a single promoter (the lac operon)
Explain how the lac operon works
When lactose is not present, repressors bind to the operators and inactivate the promoter; transcription does not proceed
When lactose is present, allolactose binds to the repressors; repressors don’t bind to operators to inactivate the promoter; transcription proceeds
Human infants and other mammals produce the enzyme _____, which digests the lactose in milk
ABC genes
What are some examples of gene control in eukaryotes?
X chromosome inactivation balances expression of X chromosome genes between female (XX) and male (XY) mammals.

SRY gene expression triggers the development of male traits in mammals.

In plants, expression of ABC master genes governs development of the specialized parts of a flower.
Bacteria control gene expression mainly by adjusting the _______
rate of transcription
Part of an operon; a DNA binding site for a repressor.
Group of genes together with a promoter–operator DNA sequence that controls their transcription.
Lac operon diagram
Small sequences of RNA nucleotides that bind to a target molecule.
Some bacterial mRNAs regulate their own translation with ______
Do bacteria control gene expression?
In bacteria, the main gene expression controls regulate gene expression in response to shifts in nutrient availability and other environmental conditions.

Prokaryotes can regulate gene expression using operons and riboswitches.
__________ and other modifications that accumulate in DNA during an individual's lifetime can be passed to offspring.
Methylation of histone proteins _______ DNA transcription.
What happens in mRNA processing?
Before eukaryotic mRNAs leave the nucleus, they are modified—spliced, capped, and finished with a poly-A tail (Section 9.3). Controls over these modifications can affect the form of a protein product and when it will appear in the cell
In eukaryotes, transcription occurs in the _____, and translation in the _______.
nucleus; cytoplasm
______ are genes that determine which parts of the body form what body parts
Homeotic genes
DNA acetlyation diagram