3.1 Flashcards by Charlotte Favre

What is a gene

a short stretch of DNA that influences a specific characteristic

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Where do organisms store their genes

on long stretches of DNA called chromosome

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What are specific forms of a gene called

alleles

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What is an allele

various, specific forms of a gene that usually vary from each other by one or a few bases

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What is a gene locus

refers to the specific position of a gene on a chromosome

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What is the diploid state,

having a pair of each kind of chromosome

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What is the haploid state

having one copy of each chromosome

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What is a homozygous gene

two copies of the same allele

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what is a heterozygous gene

two different alleles

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What is a genotype

the alleles you have a for a gene

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What is a phenotype

the trait you have as a result of your alleles

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What is always different between the alleles of a gene?

Their base sequence

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How are new alleles created

by mutations

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What are several causes for mutations

DNA replication can make mistakes, exposure to radiation, and some chemicals known as mutagens

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What do mutagens cause

tumorigenesis

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What can mutations lead to

can cause bases to be deleted from or added to the DNA sequence

can also cause a different nitrogenous base to be used in a particular place, for example guanine could be used where adenine should have been

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What is a mutation that changes on nitrogenous base in a sequence

a base substitution mutation

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What is a base substitution mutation

one that changes one nitrogenous base in a sequence

What results from base substitution

some mutations occur in a stretch of DNA that does not code for a polypeptide, and some mutations in proteins coding genes cause no change because the genetic code includes multiple codons for the sam amino acid.

if the amino acid is changes, the polypeptide formed might work differently or not at al

What is a genome

all the genetic information of an organism

name a species with more genes than humans

Rice has 25000 protein coding genes whereas humans only have 20 000

name a species with less genes than a human

Bacteria have 4000 whereas humans have 20000 protein coding genes

What is sickle cell anemia

a common genetic disease in areas where malaria is endemic

What symptoms can sickle cell anemia cause

many symptoms that vary including crisis events of extreme pain, weakness, heart attack or stroke,e pneumonia, bone malformations and deaths

Where doe sickle cell anemia occur from

one single base substitution one A instead a T

Wha gene is involved with sickle cell anemia

a stretch of DNA on chromosome 11 called HBB

What is the DNA strand that is not transcribed called

the sense strand

What does the HBB gene on chromosome 11 code for

the beta subunit of hemoglobin

What is the difference on the HBB gene in sickle cell anemia

in standard HbA, the allele reads GAG at the 6th triplet whereas in the HBS allele, it reads GTG in the same location

What happens when HBA and HBS is transcribed

HbA, GAG codes for glutamic acid the HbS mRNA, GUG becomes valine

What amino acid is replaced in sickle cell anemia

glutamic acid to valine

What is hemoglobin made of

two beta subunits and two alpha subunits and four heme groups, they form a molecule of hemoglobin

What is hemoglobin

a vital protein found in erythrocytes (red blood cells) that carries oxygen throughout the body

How many hemoglobin molecules does red blood cells contain

270 million hemoglobin molecules

What changes to the ability of the Hbs hemoglobin formed

under standard conditions, they have the same ability however under low oxygen levels, they behave differently glutamic acid interacts well with water, keeping all the hemoglobin molecules dissolves inside the erythrocyte. However, valine is hydrophobic which allows the beta subunits to join together. When the hemoglobin from HbS polymerizes into long fibres it causes two problems; its ability to carry oxygen is severely reduced and second, the long fibres poke into the cell membrane, distorting its shape and giving the red bloodd cell the characteristic curved sickle appearance.

What are the problems caused by the sickle cell shape

they can get stuck or clogged in blood vessels, causing intense pain as blood supply fails cells have to be eliminated which causes strain on the liver and a shortage of functioning red blood cells, new blood cells must be made in the bone marrow to replace the cells lost and the extra work can damage bone structure.

What is pleiotropy

when one gene has multiple effects

What is an example of pleiotropy

Sickle cell anemia

When does HbS occur

when they are both homozygous

Why is it an advantage to be a sickle cell carrier

having one HbS protects from malaria whereas having two Has leads to sickle cell anemia and does not protect frommalagia.

What type of illness is sickle cell anemia

genetic illness

Name the amino acid that is normally replaced in the beta subunit of hemoglobin in a sickle cell anemia patient.

glutamic acid

Why does the proteome of a species contain a larger number of proteins than can be coded for by the genome of the same species?

Because there is differential and development-specific expression of genes.

Which base replaces adenine in the DNA of people with this mutation in sickle cell anemia

thymine