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Biology IG > Inheritance > Flashcards

Inheritance Flashcards

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1
Q

Inheritance definition

A

hetransmission of genetic information from generation to generation

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2
Q

Gene definition

A

A length of DNA that codes for a protein

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3
Q

Allele definition

A

An alternative form of a gene (Alleles give all organisms their characteristics)

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4
Q

Chromosomes

A

Chromosomes are made of DNA which contains genetic information in the form of genes. They are located in the nucleus

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5
Q

How is the sex of the child decided

A
  • Females have the sex chromosomes XX
  • Males have the sex chromosomes XY

This means that when eggs (the female gamete) are formed, the only sex chromosome they can have is X, so all eggs have the X chromosome. When sperm are formed, however, they have a 50/50 chance of getting either the X chromosome or the Y chromosome.
Therefore, the male decides the sex of the child as only the male can pass on the Y chromosome

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6
Q

What does the sequences of bases in a gene decide?

A

The sequence of bases in a gene determines the sequence of amino acids used to make a specific protein

  • Different proteins are made of different combinations of amino acids. The sequence of amino acids in the chain determines how the chain will fold up to make the protein, so different proteins have different three-dimensional shapes. The three-dimensional shape of a protein determines its function.
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7
Q

How does DNA control cell function?

A

DNA controls cell function by controlling the production of proteins, including enzymes, membrane carriers and receptors for neurotransmitters

  • Proteins are involved in nearly every aspect of cell activity and any change in the DNA sequence (a mutation) can alter the structure and function of the resulting protein.
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8
Q

Stages of protein synthesis

A
  • Transcription(rewriting the base code of DNA into bases of RNA)
  • Translation(using RNA base sequence to build amino acids into a sequence in a protein)

the gene coding for the protein remains in
the nucleus
* messenger RNA (mRNA) is a copy of a gene
* mRNA molecules are made in the nucleus
and move to the cytoplasm
* the mRNA passes through ribosomes
* the ribosome assembles amino acids into
protein molecules
* the specific sequence of amino acids is
determined by the sequence of bases in the
mRNA

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9
Q

How are genes expressed?

A

Most body cells in an organism contain the same set of genes within their DNA, but not all of these genes are actively expressed in every cell. Expression**of a gene means whether that gene is transcribed and translated in a particular cell or not. In each type of cell, only a specific subset of genes is expressed, which means only certain proteins are produced. This selective expression of genes allows cells to perform their specialized functions and conserves energy and other resources.

  • For example, muscle cells express genes that produce proteins involved in contraction, while nerve cells express genes for proteins that transmit nerve signals.
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10
Q

What is a haploid nucleus?

A

A nucleus containing a single set of chromosomes (In humans: 23, only gametes)

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11
Q

What is a diploid nucleus?

A

A nucleus containing two sets of chromosomes (In humans: 46, every other cell in body except gametes)

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12
Q

What is in a diploid and haploid nucleus?

A

In a diploid cell, there is a pair of each type of chromosome and in a human diploid cell there are 23 pairs

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13
Q

Mitosis definition

A

nuclear division giving rise to genetically identical cells

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14
Q

Roles of mitosis

A

Since mitosis gives rise to genetically identical daughter cells, mitosis is useful when we need more of the same type of cells

Mitosis is used in:

  • Growth
    • In growth, body cells divide to form more of the same type of body cells
  • Repair of damaged tissues
  • Replacement of cells
  • Asexual reproduction
    • Asexual reproduction relies on mitosis too, because this type of reproduction does not rely on the fusion of gamete nuclei, so mitosis ensures that chromosome number is maintained.
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15
Q

Process of mitosis

A
  1. Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x - shaped chromosomes)
  2. Chromosomes line up along the centre of the cell where the copies of chromosomes separate, maintaining the chromosome number in each daughter cell
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16
Q

Stem cell definition

A

Unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions

17
Q

Meiosis definition

A

A reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells (Meiosis is involved in the production of gametes)

18
Q

How does genetic variation occur in meiosis?

A

This means that when meiosis occurs, and the chromosomes are split between the daughter cells, some daughter cells will get one of the alleles and the other daughter cells will get the other allele. Therefore, the daughter cells are not genetically identical and there is genetic variation.

19
Q

Process of meiosis

A

The number of chromosomes must behalvedwhen thegametes(sex cells) are formed. Otherwise there would be double the number of chromosomes after they join at fertilisation in the zygote (fertilized egg)

  1. Each chromosome makes identical copies of itself (forming X-shaped chromosomes)
  2. First division: chromosomes pair up along the centre of the cell, recombination occurs and then cell fibres will pull the pairs apart, each new cell will have one of each recombinant chromosome pair
  3. Second division: chromosomes will line up along the centre of the cell, cell fibres will pull them apart (as with mitosis)
  4. A total of four haploid daughter cells will be produced
20
Q

Differences between mitosis and meiosis

A
  • Mitosis two daughter cells are produced and in meiosis four daughter cells are produced
  • In mitosis daughter cells are diploid and is meiosis daughter cells are haploid
  • In mitosis daughter cells are genetically identical and in meiosis the daughter cells are genetically different
  • In mitosis only one cell division occurs while in meiosis two cell divisions occur
21
Q

Inheritance definition

A

the transmission of genetic information from generation to generation

22
Q

Genotype definition

A

the genetic make-up of an organism and in terms of the alleles present

23
Q

Phenotype definition

A

the observable features of an organism

24
Q

Homozygous definition

A

having two identical alleles of a particular gene
- two identical homozygous individuals that breed together will be pure-breeding

25
Q

Heterozygous definition

A

having two different alleles of a particular gene
- a heterozygous individual will not be pure-breeding

26
Q

Dominant allele definition

A

an allele that is expressed if it is present in the genotype

27
Q

Recessive allele definition

A

an allele that is only expressed when there is no dominant allele of the gene present in the genotype

28
Q

Codominance definition

A

a situation in which both alleles in heterozygous organisms contribute to the phenotype

29
Q

Sex linked characteristic definition

A

a feature in which the gene responsible is located on a sex chromosome and that this makes the characteristic more common in one sex than in the other

30
Q

What are pedigree diagrams?

A

Pedigree diagrams trace theinheritance patternof a specific characteristic (usually a disease)through generations of a family using symbols
- They can be used to predict the probability of someone in the family inheriting a particular trait or genetic disorder

31
Q

What are the symbols of pedigree diagrams?

A

Square is male

Circle is female

Shaded means has trait

Not shaded means doesn’t have trait

Half shaded means carrier of trait

Horizontal line means marriage

Vertical line connects parents to children

🌟 Children are listed from left to right from oldest to youngest

32
Q

What is monohybrid inheritance?

A

Monohybrid inheritanceis the inheritance of characteristics controlled by a single gene

33
Q

What is a punnett square diagram?

A

A Punnett square diagram shows thepossible combinations of allelesthat could be produced in the offspring, from this theratioof these combinations can be worked out

34
Q

How are the dominant and recessive alleles shown in punnett square?

A

Thedominant alleleis shown using a capital letter and therecessive alleleis shown using the same letter but lower case

35
Q

How to construct punnett squares?

A
  • Determine the parental genotypes
  • Select a letter that has a clearly different lower case, for example: Aa, Bb, Dd
  • Split the alleles for each parent and add them to the Punnett square around the outside
  • Fill in the middle four squares of the Punnett square to work out the possible genetic combinations in the offspring
  • You may be asked to comment on the ratio of different allele combinations in the offspring, calculate a percentage chance of offspring showing a specific characteristic or just determine the phenotypes of the offspring
  • Completing a Punnett square allows you to predict the probability of different outcomes from monohybrid crosses
36
Q

What is test cross and what does it involve?

A

Breeders can use atest crossto find out the genotype of an organism showing the dominant phenotype

  • This involves crossing the unknown individual with an individual showing the recessive phenotype
  • By looking at theratio of phenotypes in the offspring, we can tell whether the unknown individual is homozygous dominant or heterozygous
37
Q

Inheritance of blood groups rules

A

There are three alleles of the gene governing this instead of the usual two
- Alleles IAand IBare codominant, but both are dominant to IO
- I represents the gene and the superscript A, B and O represent the alleles

38
Q

Why are males more likely to have sex linked characteristics?

A

In almost all cases, there areonly alleles on the X chromosomeas theY chromosome is much smaller

  • Because malesonly have one X chromosome, they aremuch more likely to show sex-linked recessive conditions like colourblindness and haemophilia
  • Females, having two copies of the X chromosome, are likely to inherit one dominant allele that masks the effect of the recessive allele
  • A female with one recessive allele masked in this way is known as acarrier; she doesn’t have the disease, but she has a 50% chance of passing it on to her offspring

Biology IG (24 decks)

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