Be ready for Midterm (3.everything)

Question 1

Definition: genome

Answer 1

The complete DNA ‘blueprint’ for an organism

Question 2

Definition: gene

Answer 2

Pieces of DNA that influence a specific characteristic, transferred from a parent to offspring

Question 3

Definition: gametes

Answer 3

The male and the female produce special reproductive cells called gametes that carry the haploid copy of their genome produced during meiosis.

Question 4

Definition: mutations

Answer 4

Changes in the sequence of DNA. A daughter cell contain DNA that differs from the DNA in the parental cell. These changes in DNA sequence are called mutations.

Question 5

Definition: Alleles

Answer 5

Different forms of the same gene

Question 6

What makes alleles different from each other?

Answer 6

Alleles can have several or only one base different from each other

Question 7

Give an example of alleles making an impact on a person’s characteristics

Answer 7

Inheritance of sickle cell anemia

Question 8

Definition: Gene Locus

Answer 8

The specific position of a gene on a chromosome.

Question 9

What’s the difference between diploid and haploid?

Answer 9

Having a pair of each kind of chromosome is called the diploid state; having one copy of each chromosome is the haploid state.

Like most eukaryotes, humans are diploid and inherit one copy of each chromosome maternally (from the mother) and the other paternally (from the father). As a result, humans have two copies of every gene. (There is an exception related to the sex chromosomes).

Question 10

Differentiate homozygous and heterozygous:

Answer 10

You may inherit the same allele from both parents, or you may inherit two different alleles. You are homozygous for a gene if you have two copies of the same allele; you are heterozygous if you have two different alleles.

Question 11

What’s the difference between genotype and phenotype

Answer 11

The alleles you have for a gene is called your genotype. The trait you have as a result of your alleles is called your phenotype.

Question 12

How are alleles created?

Answer 12

By mutation

Question 13

What are some causes of mutation?

Answer 13

Exposure to radiation and some chemicals.

Question 14

What was the Human Genome Project?

Answer 14

The Human Genome Project began in 1990 with the aim of determining the complete sequence of the human genome and identifying every gene that it contains.

Question 15

What are some ethical issues involving the Human Genome project?

Answer 15

Knowledge of your genetic susceptibilities to certain illnesses could allow you to take steps to protect your health, but in countries without single-payer healthcare, that kind of knowledge could also be used by insurance companies to charge you more or to refuse to insure you.

Limitations of science and how this information can be used were controversial topics.

Question 16

What were the benefits of the Human Genome Project?

Answer 16

As researchers learn more about the functions of human genes and proteins, there is the potential to tailor medical treatment to the genetic profile of the individual. For example, asthma can have different genetic causes. Knowing which alleles a patient has for key genes tells doctors which medicines are likely to be effective. It is possible that affordable genetic sequencing will begin an era of ‘personalized medicine’.

Question 17

Compare the number in genes found in bacteria, human, wheat?

Answer 17

Bacteria: 4,000
(x5)
Human: 20,000
(x5)
Wheat: 100,000

Question 18

How many genes does a dog and wild mustard have?

Answer 18

19,000; 25,000 respectively

Question 19

What gene is affected with sickle cell anemia?

Answer 19

The gene involved is a stretch of DNA on chromosome 11 called HBB . It codes for the beta subunit of hemoglobin. The standard Hb A allele reads G A G at the 6th triplet of the sense DNA strand. The Hb S allele reads G T G in the same location. Otherwise, the alleles are identical.

Question 20

What happens with the wrong nucleobase in translation?

Answer 20

When the HBB locus is transcribed, the mRNA from Hb A has G A G for the 6th codon, which translates to the amino acid called glutamic acid . The mRNA copied from Hb S has the codon G U G, which codes for the amino acid valine.

Question 21

What are the consequences of sickle cell anemia?

Answer 21

When the hemoglobin from Hb S polymerizes into long fibers it causes two problems: first, its ability to carry oxygen is severely reduced, and second, the long fibers poke into the cell membrane, distorting its shape and giving the red blood cell the characteristic curved ‘sickle’ appearance.

Sickling events are triggered by low levels of oxygen in the blood, dehydration, infection, and exposure to sudden temperature changes.

Question 22

What are the genotypes for sickle cell anemia and what happens regarding protection against malaria?

Answer 22

Hb A Hb A – homozygous for normal hemoglobin, no sickling, no protection from malaria
Hb A Hb S – heterozygous, carriers of the sickle cell trait, protection from malaria
Hb S Hb S – homozygous for altered hemoglobin, sickle cell anemia, no protection from malaria

Question 23

Define chromatin, sister chromatids, chromosomes, centromere, homologous chromosomes, sex chromosomes, and autosomes .

Answer 23

chromatin: uncoiled version of DNA, visible in an electron microscope

sister chromatids: X-shaped structures visible with a light microscope. condensation of chromatids for replication

centromere: point of connection between sister chromatids

chromosome: made up of two strands that are identical to each other (chromatids)

homologous chromosomes: identical chromosomes (maternal and paternal copy) that carry the same set of genes in the same loci

sex chromosomes: chromosome that determines sex-related features in an organism (in humans: X and Y)

autosomes: other 22 pairs of chromosomes

Question 24

how many pairs of chromosomes do we have?

Answer 24

23

Question 25

How are chromosomes numbered? (what criteria)

Answer 25

length. Chromosome 1 is the longest and chromosome 22 is nearly the shortest. Chromosome 1 is approximately 250 million bases in length and carries about 2 000 genes while chromosome 22 is only 51 million bases and carries around 500 genes.

Question 26

will homologous pairs ALWAYS be identical?

Answer 26

no, Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes. There can be small differences between the nucleotide sequences of the same gene.

Question 27

What does it mean to have a diploid cell? What about haploid? Where can they be found?

Answer 27

Most of the cells in your body are diploid, meaning the nucleus contains two copies of each chromosome – 23 homologous pairs, for a total of 46 chromosomes.

Haploid nuclei, which contain only one chromosome from each pair, are found only in your gametes, or sex cells (sperm and ova).

Question 28

How are haploid cells produced?

Answer 28

Haploid cells are produced from diploid cells by meiosis.

Question 29

Each chromosome in a homologous pair is referred to as a…

Answer 29

homologue

Question 30

What’s a tetrad?

Answer 30

A structure consisting of two homologues

Question 31

Exam tip: You should be able to compare the diploid chromosome numbers of Homo sapiens, Pan troglodytes (chimpanzee, Canis familiaris (domestic dog), Oryza sativa (rice plant), and Parascaris equorum (equine roundworm.

Answer 31

Parascaris equorum (equine roundworm) 4
Oryza sativa (rice plant) 24
Homo sapiens (human) 46
Pan troglodytes (chimpanzee) 48
Canis familiaris (domestic dog) 78

Question 32

Is it possible for different species to have the same characteristic number of chromosomes? What about closely related species to have very different chromosome numbers?

Answer 32

Yes and Yes; that’s it.

Question 33

What does a karyogram do?

Answer 33

A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length.

Question 34

Differentiate karyotype from karyogram.

Answer 34

Karyotypes describe the number of chromosomes and what they look like (size bands and centromere placement). Karyograms are the study of a whole set of chromosomes arranged in pairs by size and position of the centromere.

Question 35

What are examples of functions a karyogram can accomplish?

Answer 35

A karyogram can be used to deduce the sex of an individual, to find missing or extra chromosomes, and to detect other chromosomal mutations (abnormalities)

Question 36

What happens when there is an extra chromosome? (provide emphasis on chromosome 21)

Answer 36

In most autosomes, it can fatal. However, where there are three copies of chromosome 21 present (trisomy 21), Down syndrome occurs.

Question 37

What is the weakness of karyotyping?

Answer 37

Karyotyping can diagnose only large-scale chromosomal differences. Conditions caused by differences in one or a few genes would be invisible at the level of the chromosome.

Question 38

NO QUESTION: meiosis review is on the packet given by Dr. Peano

Answer 38

NO QUESTION: meiosis review is on the packet given by Dr. Peano

Question 39

What is Gregor Johann Mendel famous for?

Answer 39

Gregor Johann Mendel (1822–1884) is famous for discovering the basic underlying principles of heredity through his work on garden pea plants (Pisum sativum).

Question 40

What are Mendel’s laws? (big one)

Answer 40

1. The law of segregation: To segregate means to divide and separate. The inheritance of each characteristic is controlled by a pair of alleles in an individual. The two alleles are separated during meiosis so that each gamete contains only one allele for each gene. Alleles are passed from one generation to the next as distinct units.
2. The law of independent assortment: The allele inherited for one trait does not affect which allele will be inherited for any other trait. A gamete contains one copy of each gene; which copy it receives during meiosis is the result of random orientation of homologous chromosomes during metaphase I.
3. The law of dominance: In an organism with two different alleles, one allele will determine the trait. The allele that determines the trait is dominant; the unexpressed allele is recessive. (There are exceptions for patterns of inheritance other than dominant–recessive, e.g. co-dominance.)

Question 41

Explain dominant allele, recessive allele, and co-dominant allele.

Answer 41

• Dominant allele: An allele that has the same effect on the phenotype whether one or two copies are present. In the heterozygous state, it will mask the presence of the recessive allele.
  Example: the allele ‘R’, which will lead to red petals when the genotype is either Rr or RR
• Recessive allele: An allele that only has an effect on the phenotype when two copies are present (in a homozygous state).
  Example: the allele ‘r’, which will lead to white petals only when the genotype is rr

Co-dominant alleles: Alleles that jointly affect the phenotype when present together, creating an intermediate or combined phenotype.
The alleles CR and CW will produce red petals when the genotype is CRCR and white when CWCW, but pink petals when CRCW

Question 42

A gene has three possible alleles. How many different genotypes can be found for this gene?

Answer 42

If there are three alleles (A, B, and C) the following six combinations are possible: AA, AB, AC, BB, BC, and CC. It is possible to have any combination of two alleles, including two of the same. It is not possible to have a copy of every allele in this case, because a diploid individual can have a maximum of two – one for each of the homologous chromosomes carrying the gene.

Question 43

How is the dominant and recessive allele represented?

Answer 43

Dominant - capital letter
recessive - lowercase letter

Question 44

What are Punnet grids/squares used for?

Answer 44

diagrams used to determine the expected ratio of genotypes and phenotypes in the offspring of parents with known genotypes.

Question 45

What’s a monohybrid cross?

Answer 45

The simplest use of a Punnett grid is a monohybrid cross, where only one characteristic is investigated.

Question 46

What happens when there is an incomplete dominance?

Answer 46

The phenotype is different than in either homozygous state and both impact the phenotype.

Question 47

What happens when there is a co-dominance?

Answer 47

Both alleles are dominant and both are expressed. A better known example of this is the human ABO blood group. Generally, the results of an incomplete dominant cross yield offspring with a blended form of the two genotypes. On the other hand, the results of a co-dominant cross will yield offspring that show both parental genotypes.

Question 48

In pea plants, flowers can either be pink (P, dominant) or white (p, recessive). If a pink flowered (Pp) and a white flowered pea plant (pp) are crossed, what is the predicted phenotype of the offspring?

Answer 48

1:1 ratio of pink to white flowers.

Question 49

what is the notation for blood?

Answer 49

IA, IB, and i.

Question 50

What does the ABO gene produce?

Answer 50

The ABO gene produces a molecule found on the surface of red blood cell membranes. (The ‘I’ in the alleles stands for ‘isoagglutinogen’ which describes the molecule.) All three alleles produce the same base molecule, but IA and IB make different additions to the molecule. These modified molecules are called antigens because they can generate an immune response in an individual to whom they are foreign.

Question 51

Which allele doesn’t produce an antigen?

Answer 51

i

Question 52

What type is the universal donor and why? What type is the universal recipient and why?

Answer 52

Because the product of the ‘i’ allele does not trigger an immune response, group O blood is known as the universal donor for blood transfusions. People with type AB blood are universal recipients because they have no antibodies to A and B in their blood and can receive red blood cells from a donor of any blood type.

Question 53

Cystic fibrosis and Huntington’s diseases are examples of….

Answer 53

Cystic fibrosis is an example of an autosomal recessive disease and Huntington’s disease (sometimes known as Huntington’s chorea) is an example of an autosomal dominant disease.

Question 54

Hemophilia is caused by an X-linked recessive allele. In the pedigree shown below, which two individuals in the pedigree must be carriers of hemophilia?

a) I-2 and II-1

b) III-2 and III-3

c) II-1 and II-2

d) I-3 and II-2

Answer 54

I-2 and II-1

Question 55

What deduction can be made about the allele for this condition from the pedigree chart?

a) It is autosomal dominant.

b) It is X-linked recessive.

c) It is Y-linked recessive.

d) It is autosomal recessive.

Answer 55

It is autosomal recessive.

Question 56

The diagram shows a pedigree.

According to the pedigree shown, which pattern of inheritance is indicated?

a) Co-dominant alleles

b) Autosomal dominant trait

c) Sex-linked recessive trait

d) Autosomal recessive trait

Answer 56

Autosomal dominant trait

Question 57

What historical events may have led to a mutation in one’s genetic code?

Answer 57

Nuclear bombing of Hiroshima in Japan, 1945.

Accidental nuclear core explosion in 1986 at the Chornobyl power station in Ukraine.